{"id":"fad54120-c1c7-432e-ab1e-41c587880c01","arxiv_id":"2504.15926","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"ErMn6Sn6 shows anomalous and topological Nernst effects, with an anomalous Nernst coefficient of 1.71 uV/K at 300 K and 3 T, comparable to other RMn6Sn6 kagome magnets.","lead":"This paper measures heat-driven transverse voltages in the Kagome magnet ErMn6Sn6 and finds a Nernst signal of 1.71 microvolts per kelvin at room temperature and 3 tesla. The value is comparable to other rare-earth Mn6Sn6 compounds, so the material is a candidate for Nernst-effect thermoelectric devices that avoid stray fields.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The 1.71 µV/K ANE value rests on a high-field decomposition that assumes the topological Nernst term vanishes at 3 T; no error bars or independent spin-structure check are provided, leaving the central quantitative claim unverified.","rationale":"After reading the manuscript in good faith, I agree with the reader's identification of the weakest link. The measured Nernst signal is large and reproducible enough to support a qualitative discovery claim, and the paper has real independent support: raw data are deposited, Onsager reciprocity is checked through ρyz/Syz, and the Hall data are consistent with prior work on isostructural compounds. However, the quantitative headline, 1.71 µV/K at 300 K and the coexisting topological Nernst peak, is obtained solely through a two-component subtraction whose central assumption (ρ_T = 0 above the transition) is unverified. No error bars are reported for the fitted slopes or intercepts, the high-field window at 300 K is only about 2-3 T, and the same decomposition is applied to the Nernst signal by analogy without an explicit field dependence for SA. A small residual topological contribution, or an anomalous term not strictly proportional to M, would be absorbed into the fitted value. The paper's own claim that ρ_T persists only in a narrow field range between 1 and 1.5 T comes from the same procedure, so it cannot serve as independent validation. This is an addressable issue rather than a fatal flaw: re-analysis of the deposited raw data with varied fit windows and explicit residuals would settle it. The conditional verdict is therefore appropriate, and I would not change it.","tokens_in":14689,"tokens_out":7477,"duration_ms":74954,"concrete_test":"Download the deposited raw data (Zenodo DOI 10.5281/zenodo.15133123) and re-fit the 250 K and 300 K Szy(H) and ρzy(H) data in two ways: (1) vary the lower cutoff of the high-field window between 2.0 T and 2.5 T with a fixed 3 T upper bound, and (2) allow a residual topological term of the form A/(1+((H-H0)/w)^2) added to the linear model in the 2-3 T window. If the extracted SAzy changes by more than about 10% between windows, or if the residual component is statistically significant, the quoted 1.71 µV/K and the topological Nernst peak are fitting artifacts. A complementary check is to confirm with neutron diffraction or the known phase diagram that the TCS/spin-chirality phase is absent at 3 T across 200-300 K.","verdict_should_be":"UNCHANGED","load_bearing_attack":"Section 2 (Figs. 3(a)-3(c) and 4(b)) obtains both the anomalous and topological Nernst coefficients from the statement: 'In the high-field saturation region where the ρT term diminishes, ρH simplifies to ρH = R0H + RS4πM,' followed by a linear fit of ρH/M versus H/M. The same decomposition is then applied to the Nernst signal Szy = S0 + SA + ST without stating a constitutive relation for SA in terms of M. The load-bearing assumption is that at 3 T the scalar-spin-chirality component is exactly zero, but this is not independently established: the field window where ρT is said to diminish is identified from the same subtraction that presupposes it, the extracted ρT is reported only as a maximum without error bars, and the 3 T upper limit leaves a narrow window above the metamagnetic transition in which M is still weakly field dependent. A residual topological term at 3 T, or a field-dependent RS, would directly shift the fitted SA and make the topological Nernst peak an artifact. The paper cites neutron work for the TCS phase but performs no spin-structure measurement on this sample at 3 T, so the 1.71 µV/K value and the topological Nernst peak are only as strong as the subtraction. This does not invalidate the qualitative observation of a large field-dependent transverse thermoelectric response, but it does underdetermine the quantitative headline.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"This manuscript reports a transport study of single-crystal ErMn6Sn6, a kagome magnet that orders in an incommensurate antiferromagnetic phase below TN ≈ 348 K and a ferrimagnetic phase below Tc ≈ 68 K. The authors measure magnetization, resistivity, magnetoresistance, Seebeck, Hall, and Nernst effects as a function of field and temperature. They decompose the Hall resistivity into normal, anomalous, and topological contributions using the standard high-field linear fit of ρH/M versus H/M, and apply the same decomposition to the Nernst signal. They report a topological Hall resistivity of about 1.2 μΩ cm at 300 K and an anomalous Nernst coefficient of 1.71 μV/K at 300 K, which they argue is comparable to other RMn6Sn6 compounds and larger than canted antiferromagnets, making ErMn6Sn6 a candidate for Nernst-based thermoelectrics. The paper includes supporting measurements for Onsager reciprocity and a data availability DOI.","tokens_in":14934,"tokens_out":6331,"duration_ms":55608,"significance":"The qualitative observation of a large field-dependent transverse thermoelectric response in an antiferromagnet at room temperature is interesting and potentially useful. The paper benefits from high-quality crystals (RRR up to ~145), a comprehensive set of transport measurements, and checks of the Onsager relation. If the decomposition is valid, the extracted values are competitive with the best reported kagome antiferromagnets. However, the quantitative separation into anomalous and topological components relies on an assumption about the high-field behavior that is not independently established in this manuscript; this limits the strength of the headline claim until the decomposition is justified or the raw total Nernst value is reported as the primary figure of merit.","major_comments":[{"comment":"The decomposition of the Hall and Nernst signals assumes that the topological contribution vanishes in the high-field saturation region at 3 T, where a linear fit of ρH/M versus H/M is performed. This is a load-bearing assumption for the extracted anomalous and topological components, but it is not independently verified for this sample. The field window between the metamagnetic transition (~1.5 T) and the 3 T upper limit is narrow, and the magnetization continues to evolve in this window. A residual topological term or a field-dependent RS at 3 T would directly shift the fitted coefficients and the subsequent Nernst decomposition. The authors should justify this assumption by, for example, providing the fitted field range and residuals, performing a sensitivity analysis with different upper field limits, or citing neutron-scattering evidence that the transverse conical spiral phase and its associated scalar spin chirality are absent at 3 T on this compound.","section":"Section 2, Figs. 3(a)-(c) and 4(b)"},{"comment":"The procedure used to extract the Nernst components is not specified. For the Hall effect, the paper gives the constitutive relations ρN = R0H and ρA = RS4πM and the linear-fit method; for the Nernst effect, the text only states that Szy = S0zy + SAzy + STzy and that 'using the methodology discussed above' the components are extracted. No functional form for SAzy in terms of M is given, so the decomposition of the Nernst data is not well-defined. The authors should provide the explicit equations and fitting procedure used for the Nernst data, including the assumed field dependence of the normal and anomalous components.","section":"Section 2, Fig. 4(b)"},{"comment":"The abstract and conclusion state that the Nernst coefficient reaches 1.71 μV/K at 300 K and 3 T, but the body text identifies 1.71 μV/K as the extracted anomalous component SAzy, not the total measured Nernst coefficient at 3 T. These are different quantities, and the wording is misleading. The paper should clearly label this value as the anomalous Nernst coefficient throughout, or alternatively quote the measured total Szy at 3 T as the headline experimental value.","section":"Abstract and Section 2, Fig. 4(c)"},{"comment":"No error bars or uncertainty estimates are reported for the extracted normal, anomalous, and topological Hall/Nernst coefficients. Since the quantitative comparison with literature values (e.g., 1.71 vs 2.2, 2, 2.21 μV/K for related compounds) is a central point, the paper should report the fitting uncertainties and, ideally, the variation of the extracted values under reasonable changes in the fitting procedure.","section":"Section 2, Figs. 3 and 4"}],"minor_comments":[{"comment":"The caption contains the repeated word 'topological' in 'topological topological Nernst coefficients'; please fix.","section":"Figure 3 caption"},{"comment":"There are minor typos: 'Nerst' should be 'Nernst' in the keywords, and 'traverse' should be 'transverse' in the abstract.","section":"Abstract and Keywords"},{"comment":"The paper describes the topological Hall and Nernst effects as appearing 'in a narrow field range between 1 – 1.5 T', but only the temperature dependence of the maximum values is shown; adding a representative field-dependent plot of ρT and ST at one temperature would make the field range of these effects directly visible.","section":"Section 2, Fig. 3(c) and text"},{"comment":"The scaling analysis that excludes skew scattering would be more convincing if the fit quality (e.g., R² value) and the comparison with the side-jump estimate were quantified in the main text or supplement.","section":"Figure S3 and associated text"}],"recommendation":"major_revision","confidential_remarks":"The manuscript's principal quantitative claim depends on a high-field decomposition that is plausible but not strongly anchored: the authors assume the topological contribution vanishes at 3 T and that the anomalous contributions scale with M, without providing an independent check on this sample. I recommend asking the authors to supply the omitted fitting details and an uncertainty analysis, or to reframe the headline around the directly measured total Nernst signal. The topic is a good fit for the journal and the raw data appear to contain a genuine field-dependent transverse thermoelectric signal."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Quick take: the Nernst measurement on ErMn6Sn6 is new, the data look internally consistent, and a room-temperature ANE of 1.71 µV/K is a useful data point for the RMn6Sn6 series. I would send it to review, with one request: harden the subtraction that separates anomalous from topological Nernst.\n\nWhat's good: the paper is a clean extension of prior work on YMn6Sn6, ScMn6Sn6, and TbMn6Sn6. The crystal quality looks good (RRR 144), the Hall, Nernst, and magnetization traces track each other, and the Onsager check between yz and zy configurations is a nice touch. The data deposit is real and the measurement section is detailed enough to reproduce. The authors also do not oversell the mechanism: they note both the static scalar-chirality and fluctuation-driven scenarios without pretending to decide. That is honest.\n\nWhere I'd push: the decomposition. The 1.71 µV/K and the topological Nernst peak both come from subtracting a linear high-field background, with the assumption that the topological term vanishes by 3 T. The paper does not show error bars, does not demonstrate that the field window is truly in the saturated region where M itself is linear in H, and does not verify the spin structure on this sample at 3 T. The neutron work is cited from another group and another crystal. That leaves the quantitative headline as only as strong as the subtraction. I don't think this invalidates the core observation—there is clearly a large field-dependent transverse thermoelectric response around 300 K—but it does mean the exact anomalous/topological split could shift if a residual topological contribution survives to 3 T or if the anomalous coefficient is field dependent. Adding error propagation, showing the fit range and residuals, and ideally a second decomposition method would settle it.\n\nMinor: the conclusion says \"promising candidate for next-generation thermoelectric devices\" while the measured Nernst coefficient is decent but not record-breaking; I'd soften that. Also the \"surpasses most canted AFM\" comparison depends on a small set of values and should stay quantitative.\n\nWho this is for: people working on transverse thermoelectrics and Kagome magnets. It is a legitimate extension, not a breakthrough. I'd accept it for review and ask for the error analysis.","headline":"A clean, useful Nernst-effect study of ErMn6Sn6 with a credible room-temperature ANE of 1.71 µV/K, but the anomalous/topological split rests on a subtraction that needs error bars and an independent spin-structure check before I'd treat the exact numbers as settled.","tokens_in":15572,"tokens_out":2131,"would_cite":true,"duration_ms":17861,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"The kagome antiferromagnet ErMn6Sn6 produces a 1.71 µV/K Nernst signal at 300 K, with both Berry-curvature and spin-chirality mechanisms, making it a candidate for room-temperature Nernst thermoelectrics.","keywords":["kagome magnet","anomalous Nernst effect","topological Nernst effect","topological Hall effect","ErMn6Sn6","spin chirality","Berry curvature","room-temperature thermoelectric"],"falsifier":"Measure the Hall and Nernst responses in ErMn6Sn6 up to fields well beyond 3 T (for example, 14 T) and compare the residual after subtracting R0H and RS4πM with the field range where neutron diffraction identifies the transverse conical spiral phase; if a nonzero 'topological' signal persists at fields where no non-coplanar spin texture exists, or vice versa, the three-component decomposition used to extract the 1.71 µV/K anomalous Nernst coefficient is not sound.","tokens_in":14423,"feed_emoji":"⚡","tokens_out":8271,"duration_ms":66118,"temperature":0.7,"pith_summary":"This paper aims to establish that the kagome magnet ErMn6Sn6 is a viable room-temperature antiferromagnetic material for Nernst-effect thermoelectrics. In its incommensurate antiferromagnetic phase, the compound shows both a topological Nernst effect, driven by spin chirality in a field-induced non-coplanar spiral state, and an anomalous Nernst effect, driven by Berry curvature near the Fermi level. The extracted anomalous Nernst coefficient reaches 1.71 µV/K at 300 K and 3 T, a value the authors argue is comparable to other RMn6Sn6 compounds and larger than most canted antiferromagnets studied before. If these assignments are correct, ErMn6Sn6 offers a transverse thermoelectric response at room temperature without the stray-field problem of ferromagnets.","feed_headline":"Kagome antiferromagnet hits 1.71 µV/K Nernst at 300 K","feed_subtitle":"Nernst value on par with the best RMn6Sn6 compounds, without ferromagnetic stray fields.","key_machinery":"The load-bearing machinery is the decomposition of the measured transverse response into three parts, ρH = R0H + RS4πM + ρT and its Nernst analogue Szy = S0zy + SAzy + STzy, together with a fitting procedure in the high-field saturation region: plotting ρH/M versus H/M and taking the slope as the normal coefficient R0 and the intercept as 4πRS, with the topological contribution as the residual. Physically, the argument rests on two mechanisms: Berry curvature near the Fermi level producing the anomalous Hall and Nernst effects, and static scalar spin chirality in the field-induced transverse conical spiral magnetic phase producing the topological Hall and Nernst effects.","core_discovery":"The central discovery claimed is that ErMn6Sn6 exhibits both the topological Nernst effect and the anomalous Nernst effect, the thermal analogues of the topological and anomalous Hall effects. Using a standard three-component decomposition of the transverse electric and thermoelectric signals into normal, anomalous, and topological terms, the authors find that the anomalous Nernst coefficient rises with temperature and reaches 1.71 µV/K at 300 K in a 3 T field. They attribute this anomalous Nernst effect to Berry curvature from massive Dirac bands of the Mn kagome lattice near the Fermi level, and they attribute the topological Hall and Nernst effects, which peak near 1.5 T between 100 and 300 K, to a field-induced transverse conical spiral phase whose non-coplanar spin texture produces a nonzero scalar spin chirality. They further report that the Nernst thermoelectric conductivity α_yz reaches 1.79 A/(m K) at 200 K and that the Onsager reciprocal relation holds between the yz and zy measurement configurations.","pith_inferences":["If the decomposition survives higher-field tests, chemical pressure or doping that shifts the Mn kagome Dirac bands closer to the Fermi level could push the anomalous Nernst coefficient above the values reported here, because the anomalous Nernst effect is hypersensitive to Berry curvature near the Fermi level.","The presence of a topological Nernst effect in ErMn6Sn6 and its reported absence in YMn6Sn6 suggests that a direct comparison of the two spiral spin structures could isolate which magnetic configuration sustains a thermal topological signal, a test the paper does not carry out.","The anomaly near 200 K in the critical field, magneto-Seebeck, and Hall/Nernst components is a promising target for temperature-dependent angle-resolved photoemission or neutron scattering to check whether the electronic structure or spin texture changes there, as the authors themselves call for further investigation."],"forward_implications":["ErMn6Sn6 can generate a transverse thermoelectric voltage at room temperature, which in principle allows Nernst-effect thermoelectric modules with a simpler orthogonal electrode geometry than Seebeck devices.","The anomalous Nernst coefficient of 1.71 µV/K at 300 K places ErMn6Sn6 in the same class as TbMn6Sn6, YMn6Sn6, and ScMn6Sn6, while its antiferromagnetic order avoids the stray fields that complicate ferromagnetic thermoelectrics.","The topological Nernst and Hall peaks near 1.5 T provide a low-field, tunable transverse response tied to the field-induced transverse conical spiral phase.","The Onsager-consistent thermoelectric conductivity of 1.79 A/(m K) at 200 K indicates that the transverse thermoelectric response is substantial in the Nernst conductivity as well as the Nernst voltage."],"supporting_citations":[{"why":"Reports the prior Hall-effect features in ErMn6Sn6 and the massive Dirac bands near the Fermi energy that motivate the Berry-curvature interpretation.","marker":"[29]"},{"why":"Supplies the 2.2 µV/K anomalous Nernst benchmark in TbMn6Sn6 and the transverse thermoelectric measurement approach.","marker":"[10]"},{"why":"Provides the 2 µV/K room-temperature anomalous Nernst benchmark in YMn6Sn6 and the comparative α(T) behaviour.","marker":"[27]"},{"why":"Provides the 2.21 µV/K anomalous Nernst value and the topological Nernst observation in ScMn6Sn6, the closest analogue for the topological Nernst effect.","marker":"[28]"},{"why":"Establishes the field-induced topological Hall effect in YMn6Sn6 via a modified spin structure with a c-axis component.","marker":"[13]"},{"why":"Supplies the competing fluctuation-driven scalar-spin-chirality mechanism used to interpret the topological Hall and Nernst signals.","marker":"[14]"},{"why":"Provides neutron-diffraction identification of the field-induced transverse conical spiral phase in ErMn6Sn6, used to assign the topological contribution.","marker":"[47]"},{"why":"Provides the Onsager reciprocal relation used to compute and validate the thermoelectric conductivity components.","marker":"[48]"}],"fun_headline_variants":["ErMn6Sn6: topological and anomalous Nernst at 300 K","Kagome antiferromagnet ErMn6Sn6 Nernst hits 1.71 µV/K","1.71 µV/K Nernst in a kagome antiferromagnet at 300 K","Room-temperature Nernst in ErMn6Sn6 kagome antiferromagnet"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The extracted topological and anomalous coefficients assume that the topological Hall and Nernst terms vanish in the high-field saturation region above about 3 T, so a linear fit of ρH/M versus H/M can isolate the normal and anomalous parts; if a topological contribution survives there, or if the anomalous term is not strictly proportional to magnetization, the 1.71 µV/K figure and the topological peak are fitting artifacts.","fun_headline_variants_meta":{"raw":{"variants":["ErMn6Sn6: topological and anomalous Nernst at 300 K","Kagome antiferromagnet ErMn6Sn6 Nernst hits 1.71 µV/K","1.71 µV/K Nernst in a kagome antiferromagnet at 300 K","Room-temperature Nernst in ErMn6Sn6 kagome antiferromagnet"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.001026,"raw_usage":{"total_tokens":4346,"prompt_tokens":990,"completion_tokens":3356,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":606,"completion_tokens_details":{"reasoning_tokens":3255}},"tokens_in":606,"tokens_out":3356,"duration_ms":22915,"temperature":1.0,"reasoning_tokens":3255,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-16T11:14:00.663707+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the Hall and Nernst responses in ErMn6Sn6 up to fields well beyond 3 T (for example, 14 T) and compare the residual after subtracting R0H and RS4πM with the field range where neutron diffraction identifies the transverse conical spiral phase; if a nonzero 'topological' signal persists at fields where no non-coplanar spin texture exists, or vice versa, the three-component decomposition used to extract the 1.71 µV/K anomalous Nernst coefficient is not sound.","supporting_citations":[{"cited_title":"Topological Nernst effect in a three-dimensional skyrmion-lattice phase","cited_arxiv_id":null,"evidence_quote":"Reports the prior Hall-effect features in ErMn6Sn6 and the massive Dirac bands near the Fermi energy that motivate the Berry-curvature interpretation."},{"cited_title":"Exchange-biased topological transverse thermoelectric effects in a Kagome ferrimagnet","cited_arxiv_id":null,"evidence_quote":"Supplies the 2.2 µV/K anomalous Nernst benchmark in TbMn6Sn6 and the transverse thermoelectric measurement approach."},{"cited_title":"Anomalous Nernst effect beyond the magnetization scaling relation in the ferromagnetic Heusler compound Co2MnGa","cited_arxiv_id":null,"evidence_quote":"Provides the 2 µV/K room-temperature anomalous Nernst benchmark in YMn6Sn6 and the comparative α(T) behaviour."},{"cited_title":"Topological Nernst and topological thermal Hall effect in rare-earth kagome ScMn6Sn6","cited_arxiv_id":null,"evidence_quote":"Provides the 2.21 µV/K anomalous Nernst value and the topological Nernst observation in ScMn6Sn6, the closest analogue for the topological Nernst effect."},{"cited_title":"Progress and prospects in magnetic topological materials","cited_arxiv_id":null,"evidence_quote":"Establishes the field-induced topological Hall effect in YMn6Sn6 via a modified spin structure with a c-axis component."},{"cited_title":"Spin Chirality Fluctuations and Anomalous Hall Effect in Itinerant Ferromagnets","cited_arxiv_id":null,"evidence_quote":"Provides neutron-diffraction identification of the field-induced transverse conical spiral phase in ErMn6Sn6, used to assign the topological contribution."},{"cited_title":"Large topological Hall effect in the non-collinear phase of an antiferromagnet","cited_arxiv_id":null,"evidence_quote":"Provides the Onsager reciprocal relation used to compute and validate the thermoelectric conductivity components."}],"review_version":1}