Singular angular magnetoresistance in a magnetic nodal semimetal.

Transport coefficients of correlated electron systems are often useful for mapping hidden phases with distinct symmetries. Here we report a transport signature of spontaneous symmetry breaking in the magnetic Weyl semimetal CeAlGe system in the form of singular angular magnetoresistance (SAMR). This angular response exceeding 1000% radian-1 is confined along the high symmetry axes with a full width at half maximum reaching to less than 1° and is tunable via isoelectronic Ge/Si substitution. The SAMR phenomena is explained theoretically as a consequence of controllable high resistance domain walls, arising from the breaking of magnetic point group symmetry strongly coupled to a nearly nodal electronic structure. This study indicates ingredients for engineering magnetic materials with unprecedented angular sensitivity by lattice and site symmetries.