Chiral symmetry and magnetism in a 3D Kagome lattice: RPt$_2$B (R = La and Nd) prototype crystals

Chirality in crystals arises from the exclusive presence of proper symmetry operations, such as rotations and screw axes, while lacking improper operations like inversion, mirror planes, and roto-inversions. Crystallographic chirality is expected to be coupled with magnetic responses in magnetically active chiral compounds. Therefore, this study investigates the interplay between structural chirality and magnetic ordering in the rare-earth platinum boride family, RPt$_2$B, where R denotes lanthanide elements. Our results show that the R sites structurally form a chiral three-dimensional Kagome lattice, which can lead to magnetic frustration resolved through chiral antiferromagnetic orderings in conjunction with chiral symmetry. Symmetry analysis reveals that these chiral antiferromagnetic states are low-energy states, competing with higher-in-energy (001) ferromagnetic configuration. We also identified Kramers-type Weyl points in the electronic structure without magnetic response. In the magnetically active chiral compound NdPt$_2$B, Zeeman splitting lifts degeneracies at the high-symmetry points; however, Weyl points persist due to the breaking of time-reversal (T) and inversion (P) symmetries. We also estimate the anomalous Hall conductivity, a measurable observable of the allowed topological features finding a value of $\sigma_{xy} = 293$ S$\cdot$cm$^{-1}$ comparable with another Kagome magnetic materials like Mn$_3$PtN and FeSn, for example. This study elucidates the intricate interplay among chirality, magnetism, and topology in rare-earth Kagome materials.