  Extensive studies of electron transport in Dirac materials have shown
positive magneto-resistance (MR) and positive magneto-thermopower (MTP) in a
magnetic field perpendicular to the excitation current or thermal gradient. In
contrast, measurements of electron transport often show a negative longitudinal
MR and negative MTP for a magnetic field oriented along the excitation current
or thermal gradient; this is attributed to the chiral anomaly in Dirac
materials. Here, we report a very different magneto-thermoelectric transport
behavior in the massive Dirac material ZrTe5. Although thin flakes show a
commonly observed positive MR in a perpendicular magnetic field, distinct from
other Dirac materials, we observe a sharp negative MTP. In a parallel magnetic
field, we still observe a negative longitudinal MR, however, a remarkable
positive MTP is observed for the fields parallel to the thermal gradients. Our
theoretical calculations suggest that this anomalous magneto-thermoelectric
behavior can be attributed to the screened Coulomb scattering. This work
demonstrates the significance of impurity scattering in the electron transport
of topological materials and provides deep insight into the novel
magneto-transport phenomena in Dirac materials.
