Giant planar Hall effect in topological metals

Much excitement has been generated recently by the experimental observation of the chiral anomaly in condensed matter physics. This manifests as strong negative longitudinal magnetoresistance and has so far been clearly observed in Na₃Bi, ZrTe₅, and GdPtBi. In this Rapid Communication, we point out that the chiral anomaly must lead to another effect in topological metals, the giant planar Hall effect (GPHE), which is the appearance of a large transverse voltage when the in-plane magnetic field is not aligned with the current. Moreover, we demonstrate that the GPHE is closely related to the angular narrowing of the negative longitudinal magnetoresistance signal, observed experimentally.