We demonstrate that a multi-k incommensurate magnetic state in the Weyl semimetal CeAlGe gives rise to singular angular magnetoresistance (SAMR), an electrical-transport signature that detects the magnetic-field direction with exceptional precision. In contrast, the sister compound CeAlSi shows neither multi-k order nor SAMR. Both phenomena emerge upon ∼57% Ge substitution in CeAlSi1−xGex and coincide with electronic-structure changes that soften the single-ion in-plane anisotropy and enhance Weyl-mediated magnetic interactions. These results reveal a direct connection between band topology, electronic transport, and collective magnetism in Weyl semimetals.
@article{arxiv.2509.18398,
title = {Incommensurate magnetic order drives singular angular magnetoresistance in a Weyl semimetal},
author = {X. Yao and P. Chen and R. Verma and X. Zhao and H. -Y. Yang and L. DeBeer-Schmitt and A. A. Aczel and C. -M. Wu and D. Alba Venero and T. Ohhara and K. Munakata and M. Takahashi and Y. Noda and A. Bansil and B. Singh and P. Nikolić and F. Tafti and J. Gaudet},
journal= {arXiv preprint arXiv:2509.18398},
year = {2026}
}