  The unique band structure in topological materials frequently results in
unusual magneto-transport phenomena, one of which is in-plane longitudinal
negative magnetoresistance (NMR) with the magnetic field aligned parallel to
the electrical current direction. This NMR is widely considered as a hallmark
of chiral anomaly in topological materials. Here we report the observation of
in-plane NMR in the topological material ZrTe5 when the in-plane magnetic field
is both parallel and perpendicular to the current direction, revealing an
unusual case of quantum transport beyond the chiral anomaly. We find that a
general theoretical model, which considers the combined effect of Berry
curvature and orbital moment, can quantitatively explain this in-plane NMR. Our
results provide new insights into the understanding of in-plane NMR in
topological materials.
