{"id":"4a1cb416-4eaa-4787-bf0b-90885038e13c","arxiv_id":"2411.14140","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":1,"one_line_summary":"A 9-tesla field reduces the resistance of the half-Heusler crystal HoAuSn by up to 99%, which the authors attribute to a field-induced transition into a Weyl semimetal.","lead":"This paper reports that the electrical resistance of the magnetic crystal HoAuSn drops by up to 99% when a 9-tesla magnetic field is applied, an effect that persists to 20 K, well above its 1.9 K magnetic ordering temperature. The authors propose that the field rearranges the material's electronic bands and creates Weyl points, which changes how easily current flows.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The Weyl mechanism hinges on the unvalidated identification of the 9 T state with the zero-field FM DFT state; no calculation or transport signature directly links the measured field-induced state to Weyl nodes.","rationale":"The reader's weakest assumption is exactly the point on which the paper's mechanism rests: the zero-field ferromagnetic DFT band structure is used as a proxy for the actual electronic structure at 9 T. I agree that this is the single most load-bearing assumption. The paper's transport data are new and the angular dependence is reported in detail, but the Weyl-point evidence comes only from GGA+U+SOC calculations of a hypothetical collinear FM state, with no field-dependent calculation and no experimental Fermi-surface or Hall measurement tying carrier-density changes to Weyl nodes. I also note a secondary tension: the large negative MR is present for transverse configurations, so a chiral-anomaly-based explanation is incomplete; however, the paper does not rely solely on chiral anomaly, invoking instead field-induced band reconstruction and spin-scattering suppression. This makes the missing link even more important: without a validated field-dependent band structure, the mechanism remains speculative. The proposed test, computing at the measured 9 T magnetization, would settle whether the Weyl nodes survive under the experimentally relevant conditions. Because the reader already marked the verdict CONDITIONAL with moderate confidence, my independent read supports that same verdict rather than moving it; the condition should specify that the 9 T state must be demonstrated to match the calculated FM configuration.","tokens_in":7948,"tokens_out":4786,"duration_ms":49326,"concrete_test":"Perform fixed-spin-moment DFT (or add a Zeeman exchange field) constrained to the magnetization value measured at 9 T in Fig. 1f for the same field directions used in transport, and search for Weyl points within a few meV of the Fermi level. Repeat for the full collinear FM moment as a control; if the nodes disappear or move far from EF at the measured moment, the central mechanism is falsified.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim requires that the state accessed at 9 T is close to the collinear ferromagnetic configuration used in the GGA+U+SOC band calculations (Sec. 3, Fig. 4c). The experiments show zero-field AFM order below TN ≈ 1.9 K, a metamagnetic transition near 4 T (Fig. 1f), and magnetization only gradually approaching saturation at 9 T; no calculation or measurement establishes that the 9 T state has the full collinear FM moment assumed in Fig. 4c. The DFT also uses a hand-set Ueff = 8 eV with no validation against the measured moment or gap. Moreover, the transport evidence does not independently support Weyl nodes: the large negative MR appears for B perpendicular to the current, whereas chiral-anomaly negative longitudinal MR is specific to B || J; the proposed alternative 'suppressed spin scattering' is qualitative. Thus the load-bearing step, 'magnetic field induces a Weyl point,' is supported only by an unvalidated zero-field FM band structure, not by a field-dependent calculation or by a field-dependent carrier-density/Hall signature. If the 9 T state is only partially polarized or retains AFM canting, the Weyl points may not exist near EF and the observed negative MR could be explained by a generic field-driven insulator-to-metal transition.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports single-crystal growth, magnetization, resistivity, and angular-dependent magnetoresistance measurements on the antiferromagnetic half-Heusler HoAuSn. A negative MR of up to 99% at 9 T is observed, robust up to 20 K, and present for multiple field-current geometries. GGA+U+SOC band-structure calculations of a ferromagnetic state with magnetization along [111], [110], and [001] show Weyl points near the Fermi level, which the authors interpret as evidence that the applied field induces a transition from a trivial semimetal to a Weyl semimetal and thereby suppresses spin scattering and produces the large negative MR.","tokens_in":8184,"tokens_out":6669,"duration_ms":57101,"significance":"The transport data are carefully measured, and the observation of a 99% negative MR at 9 T, with clear angular dependence and persistence far above TN, is of empirical interest for antiferromagnetic half-Heuslers. The paper's value lies mainly in the magnetotransport dataset and the identification of HoAuSn as a candidate field-induced Weyl semimetal; the calculated Fermi surfaces and density of states provide qualitative support for band reconstruction. However, the central mechanism is not demonstrated: the assumed zero-field FM state is used as a proxy for the 9 T state, and no transport signature (Hall effect, longitudinal-only negative MR, quantum oscillations) directly links the negative MR to Weyl nodes. If the mechanism were established, the result would be significant for field-induced topological transitions in magnetic half-Heuslers; as it stands, it is a candidate mechanism with suggestive but incomplete evidence.","major_comments":[{"comment":"The identification of the 9 T field-induced state with the zero-field collinear FM band structure of Fig. 4c is not justified: HoAuSn is antiferromagnetic below TN=1.9 K, and Fig. 1f shows a metamagnetic transition near 4 T with magnetization only gradually approaching saturation at 9 T. No field-dependent calculation or high-field magnetization comparison (e.g., the calculated FM moment vs. M(9 T)) is provided. If the 9 T state is only partially polarized or canted, the Weyl points in the Γ-L path may not exist near the Fermi level, and the central claim that the magnetic field induces the Weyl point collapses.","section":"Sec. 3, Fig. 4c; Sec. 2, Fig. 1f"},{"comment":"The GGA+U+SOC calculations use a hand-set Ueff = 8 eV for Ho 4f electrons with no sensitivity analysis or validation against the measured magnetic moment, band gap, or photoemission. The presence and energy position of Weyl points in the FM state are sensitive to Ueff and to the treatment of the 4f electrons; without such validation, the calculation cannot establish that Weyl points appear near EF specifically in the high-field state.","section":"Sec. 2, Sec. 3 Fig. 4 caption"},{"comment":"The transport evidence does not demonstrate Weyl nodes: the paper reports 99% negative MR for B||J and about 90% for B⊥J, yet the chiral-anomaly scenario predicts a pronounced longitudinal-transverse distinction, and the observed negative MR in transverse geometry is attributed to an unquantified increase in carrier concentration from the reconstructed band structure. No Hall measurement, carrier-density analysis, or quantitative magnetotransport model is provided, so the data cannot discriminate between the proposed Weyl mechanism and a generic field-driven insulator-to-metal transition in a canted or partially polarized state.","section":"Sec. 3, Figs. 2b-2d; Conclusion"},{"comment":"The attribution of the two-fold AMR symmetry to 'chiral anomalies' is speculative: no symmetry analysis or model calculation connects the chiral anomaly to the observed two-fold angular dependence, and the four-fold terms are fitted phenomenologically. At minimum, the angular-dependent data should be compared with expectations for a field-induced Weyl semimetal with the relevant magnetic point group, or the symmetry statement should be withdrawn.","section":"Sec. 3, Fig. 3"}],"minor_comments":[{"comment":"Reference numbering errors: the Cd3As2 negative-MR work is cited as [29] but reference [29] is the MnFeGe paper (Tang et al.); the Cd3As2 nanowire paper is reference [30]. Similarly, BaMn2Bi2 is cited as [30] but appears as reference [31], and EuMnSb2 is cited as [31] but is reference [32]. The 'half-heusler alloy TbPbBi[25]' citation should be [26] (and the compound name should read TbPdBi).","section":"Sec. 3, paragraph on negative-MR materials"},{"comment":"Typo: 'extractd' should be 'extracted'.","section":"Fig. 1c"},{"comment":"The phrase 'magnetics fields' should be 'magnetic fields'.","section":"Abstract and Sec. 2"},{"comment":"The calculation for the zero-moment state is referred to both as 'non-magnetic (NM)' (text) and 'paramagnetic' (Fig. 4 caption); please use one term consistently.","section":"Fig. 4 caption and Sec. 3"},{"comment":"The current direction for the (001)-plane measurements shown in Fig. S4 is not specified in the main text; please state the crystallographic direction of the current in those measurements.","section":"Sec. 3, angular dependence discussion"}],"recommendation":"major_revision","confidential_remarks":"The manuscript is a follow-up to Ueda et al. (ref. [25]) on the same compound; its incremental contribution is the angular dependence study and the AMR symmetry, but the mechanism discussion largely repeats the earlier interpretation. The main technical worry is the unvalidated FM proxy for the 9 T state; I would advise the editor to require either field-dependent calculations or direct high-field magnetization/Hall evidence before publication. The paper fits the journal's scope as a materials-science transport study."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Colleague,\n\nShort version: this is a careful transport study of HoAuSn with a comprehensive angular dependence dataset, and the 99% negative MR is real as far as I can tell from the text. But the paper's central mechanism—field-induced Weyl semimetal—rests on a zero-field collinear FM band calculation with a hand-set Hubbard U, and no measurement or calculation actually ties the 9 T state to that band structure. The stress-test note captures this correctly.\n\nWhat's new: the systematic AMR measurements with rotations in three planes, the persistence of negative MR to 20 K, and the evolution of AMR symmetry from M-shaped to W-shaped. These data are a genuine addition to the half-Heusler negative-MR literature. The paper also clearly builds on Ueda et al. [25] and Zhu et al. [26], so the mechanism itself is not new; the contribution is the specific compound and the angular resolution.\n\nWhere it gets soft: the DFT is done in the FM state with M along [111], [110], [001], but the experimental zero-field state is AFM, and the metamagnetic transition at 4 T means the 9 T state is likely not a simple collinear FM. The authors don't compute a field-dependent band structure or even a canted state. The Ueff=8 eV is a free parameter, and there's no check against the measured magnetic moment or the semiconducting gap. On the transport side, they see negative MR for all orientations, including B perpendicular to J, so chiral anomaly cannot be the whole story. The paper itself mentions 'suppressed spin scattering' in the abstract, which is qualitative and not tied to any calculation. There's no Hall data or carrier-density measurement, and no fitting of any equation to the MR to test a mechanism. The citation pattern is fine—the prior work is cited—but the reference numbering has errors (e.g., [25] appears in the text where [26] might be meant, and [29] is used twice for different papers). Minor: error bars aren't shown in the figures.\n\nOverall: the experimental data are solid and worth having, but the interpretation is overclaimed. A serious referee should ask for either a direct probe of the field-induced state (Hall, specific heat, or a field-dependent DFT) or a more careful phrasing of the mechanism. I'd send this to review, with the expectation of major revision on the interpretation.\n\nRecommendation: engage with it—send to a good referee, but make sure they push on the missing Hall and the unvalidated FM assumption.","headline":"New angular-dependent transport data on HoAuSn, but the field-induced Weyl mechanism is asserted, not demonstrated.","tokens_in":8770,"tokens_out":5000,"would_cite":true,"duration_ms":41110,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":["75.47.-m","71.20.-b","71.15.Mb"],"model":"deepseek-v4-flash","headline":"In the antiferromagnetic half-Heusler HoAuSn, a 9 T magnetic field reconstructs the band structure from a trivial semimetal into a Weyl semimetal, creating Weyl points near the Fermi level and raising the carrier concentration, which…","keywords":["negative magnetoresistance","half-Heusler compounds","Weyl semimetal","field-induced band structure change","antiferromagnetism","HoAuSn","angular magnetoresistance","first-principles calculations"],"falsifier":"Measure the Hall coefficient across the metamagnetic transition near 4 T: the field-induced Weyl scenario predicts a sharp increase in carrier concentration, visible as a jump in the Hall signal at the same field where the resistivity begins its two-order-of-magnitude drop; if the carrier density stays flat while the resistivity collapses, the band-reconstruction mechanism would be falsified.","tokens_in":7711,"feed_emoji":"🧲","tokens_out":11841,"duration_ms":92796,"temperature":0.7,"pith_summary":"HoAuSn, an antiferromagnetic half-Heusler with a Néel temperature of 1.9 K, exhibits a negative magnetoresistance of up to 99% at 9 T, an effect that survives to 20 K and does not require the magnetic field to be parallel to the current. The paper argues that this large negative magnetoresistance is not an ordinary scattering effect but the transport signature of a magnetic-field-driven band reconstruction. Transport measurements combined with first-principles calculations are used to propose that the field transforms HoAuSn from a trivial semimetal into a Weyl semimetal, with Weyl points appearing near the Fermi level, a larger Fermi surface, and a higher density of states at the Fermi energy. If this picture is right, HoAuSn provides a concrete antiferromagnetic half-Heusler in which a large negative magnetoresistance and a field-induced topological band transition are directly linked.","feed_headline":"9 T field creates Weyl points and 99% negative magnetoresistance","feed_subtitle":"A 9 T field turns antiferromagnetic HoAuSn into a Weyl semimetal and produces 99% negative magnetoresistance.","key_machinery":"The central object is the field-induced Weyl point: in the ferromagnetic band structure calculated with GGA+SOC+U ($U_{\\mathrm{eff}}=8$ eV), Weyl points appear in the $\\Gamma$–$L$ path near the Fermi level, and Wilson-loop calculations confirm their existence for magnetization along $[111]$, $[110]$, and $[001]$. This object carries the argument because it connects the applied magnetic field to transport: spin polarization from the field splits bands, closes the gap, enlarges the Fermi surface, raises the density of states at the Fermi level, and thereby increases carrier concentration and suppresses spin scattering. The angular-dependence measurements, in which the field is rotated between $[111]$, $[1\\bar{1}0]$, and $[11\\bar{2}]$ with current fixed along $[1\\bar{1}0]$, together with the two-fold and four-fold AMR symmetry fits, are the experimental counterpart that ties the Weyl-point scenario to the observed negative MR.","core_discovery":"The paper's central claim is that in HoAuSn a sufficiently strong magnetic field (on the order of 9 T) reconstructs the electronic band structure, taking the material from a trivial semimetal to a Weyl semimetal and producing a negative magnetoresistance as large as 99%. In the non-magnetic calculation HoAuSn is a trivial semimetal with a small hole pocket near $\\Gamma$ and an electron pocket near $X$; in the ferromagnetic calculation, with magnetization along $[111]$ (and also for $[110]$ and $[001]$), Weyl points appear on the $\\Gamma$–$L$ path, the Fermi-surface area grows, and the density of states at the Fermi level increases. The paper interprets the enlarged Fermi surface and increased carrier concentration as the reason the resistivity drops sharply under field, and it connects the angular dependence of the magnetoresistance, including the two-fold and four-fold components of the anisotropic magnetoresistance, to the same field-induced band change.","pith_inferences":["A testable extension not performed in the paper is to look for the enlarged Fermi surface directly via quantum oscillations: the ferromagnetic band calculation predicts additional or shifted Shubnikov–de Haas frequencies above the metamagnetic transition, which could be checked by high-field torque or resistivity measurements.","The paper assumes a particular collinear ferromagnetic moment direction; an implication left implicit is that the angular dependence of the negative MR could be inverted to infer the actual moment direction at 9 T, effectively using transport as a magnetic-structure probe.","If the Weyl points really sit near the Fermi level, HoAuSn should also show other topological signatures, such as an anomalous Hall effect or a chiral-anomaly contribution in longitudinal fields; measuring these would provide independent cross-checks of the scenario.","The framework suggests a correlation across antiferromagnetic half-Heuslers between the rare-earth metamagnetic transition field and the onset field of the large negative MR; a systematic series of compounds could test this prediction."],"forward_implications":["HoAuSn becomes a transport-based example of a magnetic-field-driven topological transition in an antiferromagnetic half-Heusler, with the 99% negative magnetoresistance serving as a bulk probe of the Weyl-point formation.","Because the negative MR persists to 20 K, well above the 1.9 K Néel temperature, the field-induced band reconstruction is robust against loss of long-range magnetic order, and the effect should also be observable in the paramagnetic regime.","The angular dependence of the high-field MR, with two-fold and four-fold components, provides a symmetry-based fingerprint that can be used to identify field-induced Weyl points in other antiferromagnetic half-Heuslers.","Since the effect appears for all measured angles between field and current, its origin is distinct from the conventional longitudinal chiral-anomaly negative MR and points to a more general band-structure-driven mechanism.","Replacing Ho with other lanthanide rare earths should tune the field scale and temperature window of the negative magnetoresistance, offering a materials-design route to even larger effects."],"supporting_citations":[{"why":"Reports the field-induced Weyl semimetal mechanism and large angle-independent negative magnetoresistance in the same magnetic half-Heusler family, providing the template this paper extends to HoAuSn.","marker":"[25]"},{"why":"Provides the theoretical framework for creating Weyl fermions with a magnetic field, the concept the paper invokes for the field-induced transition.","marker":"[34]"},{"why":"Reviews magnetically induced topological states and supports the interpretation that a magnetic field can drive a trivial semimetal into a Weyl semimetal.","marker":"[33]"},{"why":"Establishes chiral-anomaly-induced large negative magnetoresistance in half-Heusler RPtBi compounds, the family context for HoAuSn.","marker":"[19]"},{"why":"Reports negative longitudinal magnetoresistance as evidence of a possible chiral anomaly in the half-Heusler antiferromagnet DyPdBi, a comparison system.","marker":"[24]"},{"why":"Documents the 63% negative magnetoresistance in Cd3As2 nanowires as a benchmark chiral-anomaly system that the paper compares against.","marker":"[30]"},{"why":"Supplies the plane-wave total-energy code used for all first-principles band-structure calculations.","marker":"[27]"},{"why":"Supplies the generalized-gradient-approximation functional used in the GGA+SOC+U calculations.","marker":"[28]"}],"fun_headline_variants":["99% negative MR in HoAuSn from field-induced Weyl points","Field-induced Weyl points yield 99% negative magnetoresistance","Angular negative MR tied to field-induced Weyl semimetal state","HoAuSn: 9 T field makes Weyl points, 99% negative MR","Antiferromagnetic HoAuSn shows 99% negative MR via field-induced Weyl points"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The argument rests on assuming that a 9 T applied field puts HoAuSn into the collinear ferromagnetic state used in the calculation, with moments along $[111]$, $[110]$, or $[001]$, even though the measured zero-field ground state is antiferromagnetic below 1.9 K with a metamagnetic transition near 4 T, and no measurement or calculation shows that 9 T actually produces that ferromagnetic configuration.","fun_headline_variants_meta":{"raw":{"variants":["99% negative MR in HoAuSn from field-induced Weyl points","Field-induced Weyl points yield 99% negative magnetoresistance","Angular negative MR tied to field-induced Weyl semimetal state","HoAuSn: 9 T field makes Weyl points, 99% negative MR","Antiferromagnetic HoAuSn shows 99% negative MR via field-induced Weyl points"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000505,"raw_usage":{"total_tokens":2456,"prompt_tokens":925,"completion_tokens":1531,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":541,"completion_tokens_details":{"reasoning_tokens":1428}},"tokens_in":541,"tokens_out":1531,"duration_ms":11929,"temperature":1.0,"reasoning_tokens":1428,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-12T15:29:51.178898+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the Hall coefficient across the metamagnetic transition near 4 T: the field-induced Weyl scenario predicts a sharp increase in carrier concentration, visible as a jump in the Hall signal at the same field where the resistivity begins its two-order-of-magnitude drop; if the carrier density stays flat while the resistivity collapses, the band-reconstruction mechanism would be falsified.","supporting_citations":[{"cited_title":"and Tokura Y ., Colossal negative magnetoresistance in field-induced Weyl semimetal of magnetic half-Heusler compound, Nature Communications, 2023, 14(1): 6339","cited_arxiv_id":null,"evidence_quote":"Reports the field-induced Weyl semimetal mechanism and large angle-independent negative magnetoresistance in the same magnetic half-Heusler family, providing the template this paper extends to HoAuSn."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Provides the theoretical framework for creating Weyl fermions with a magnetic field, the concept the paper invokes for the field-induced transition."},{"cited_title":"and Yan B., Magnetically induced, Nature Materials, 2016, 15(11): 1149","cited_arxiv_id":null,"evidence_quote":"Reviews magnetically induced topological states and supports the interpretation that a magnetic field can drive a trivial semimetal into a Weyl semimetal."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Establishes chiral-anomaly-induced large negative magnetoresistance in half-Heusler RPtBi compounds, the family context for HoAuSn."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Reports negative longitudinal magnetoresistance as evidence of a possible chiral anomaly in the half-Heusler antiferromagnet DyPdBi, a comparison system."},{"cited_title":"and Yu D.-P., Giant negative magnetoresistance induced by the chiral anomaly in individual Cd3As2 nanowires, Nature Communications, 2015, 6(1): 10137","cited_arxiv_id":null,"evidence_quote":"Documents the 63% negative magnetoresistance in Cd3As2 nanowires as a benchmark chiral-anomaly system that the paper compares against."},{"cited_title":"and Furthmuller J., Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set, Physical Review B, 1996, 54(16): 11169","cited_arxiv_id":null,"evidence_quote":"Supplies the plane-wave total-energy code used for all first-principles band-structure calculations."},{"cited_title":"P., Burke K","cited_arxiv_id":null,"evidence_quote":"Supplies the generalized-gradient-approximation functional used in the GGA+SOC+U calculations."}],"review_version":1}