Planar Hall effect with sixfold oscillations in a Dirac antiperovskite

The planar Hall effect (PHE), wherein a rotating magnetic field in the plane of a sample induces oscillating transverse voltage, has recently garnered attention in a wide range of topological metals and insulators. The observed twofold oscillations in rho(yx) as the magnetic field completes one rotation are the result of chiral, orbital, and/or spin effects. The antiperovskites A(3)BO (A = Ca, Sr, Ba; B = Sn, Pb) are topological crystalline insulators whose low-energy excitations are described by a generalized Dirac equation for fermions with total angular momentum J = 3/2. We report unusual sixfold oscillations in the PHE of Sr3SnO, which persisted nearly up to room temperature. Multiple harmonics (twofold, fourfold, and sixfold), which exhibited distinct field and temperature dependencies, were detected in rho(xx) and rho(yx). These observations are more diverse than those in other Dirac and Weyl semimetals and point to a richer interplay of microscopic processes underlying the PHE in the antiperovskites.