Large magnetoresistance and large magnetothermopower effect in the Dirac material EuMn_0.8Sb₂

In this article, the structure, transport and magnetic properties were studied in details for EuMn_0.8Sb₂ crystals with the orthorhombic structure and Mn deficiencies. It was found that the temperature dependence of the resistivity exhibits a metallic behavior in the whole measuring temperature range, different from that in the crystals without Mn deficiencies. A large positive magnetoresistance (MR) (∼127% at 2 K and  ∼25% at 300 K, in 9 T field) was observed, which can be ascribed to the combination of semiclassical MR and quantum limit MR of Dirac electrons. We also observed the high mobility of the carriers and large magnetothermopower effect at low temperatures, and two magnetic transitions emerging at  ∼24 K and  ∼10 K, respectively, corresponding to the antiferromagnetic ordering and canted arrangement of the Eu moments. Our findings shed new light on the intrinsic properties of EuMn_0.8Sb₂ and demonstrate the existence of Dirac fermions.