The interplay between incommensurate magnetism and singular angular magnetoresistance in a Weyl semimetal

Magnetic Weyl semimetals provide a fertile ground for exploring the interplay between topological electronic structures and collective magnetism. We report that a multi-k incommensurate magnetic order in the compound CeAlGe is responsible for its singular angular magnetoresistance (SAMR)—a striking transport signature that detects the magnetic-field direction with extreme sensitivity. In contrast, the isostructural compound CeAlSi, which lacks the incommensurate order is devoid of SAMR. By tracking the series CeAlSi_{1-x}​Ge_x​, we identify a crossover near x=57% where the in-plane anisotropy softens and Weyl-mediated magnetic interactions emerge. The resulting magnetic state couples strongly to the topological band structure, producing sharp anisotropic transport responses. These findings establish a direct connection between incommensurate magnetism and anisotropic Weyl transport, opening opportunities for directional quantum sensing applications.