Two-fold symmetric anomalous angular magnetoresistance of the proposed tetragonal Weyl semimetal CeAlGe

A noncentrosymmetric tetragonal compound CeAlGe, a proposed type-II Weyl semimetal, orders antiferromagnetically below 5 K in zero magnetic field. In the magnetically ordered state, the moment lies in the tetragonal ab-plane and thus the M(H) data show a four-fold symmetry along the principal directions in the ab-plane. However, anomalously robust and complex two-fold symmetry is observed in the angular dependence of resistivity and magnetic torque data in the magnetically ordered state once the field is swept in the ab-plane. This two-fold symmetry is independent of temperature and field-hystereses. We will show that this anomalous behavior is the result of the complex magnetic structures and the phase transition between them, and that the critical field of that phase transition can be tuned by an Al deficiency.