Magnetotransport and electronic structure of EuAuSb: A candidate antiferromagnetic Dirac semimetal

We have investigated the magnetic, thermodynamic, and electrical transport properties of EuAuSb single crystals as well as carrying out band structure calculations. The powder x-ray diffraction data confirm that EuAuSb crystallizes in ZrBeSi-type hexagonal structure with space group P6₃/mmc. The magnetic measurements reveal an antiferromagnetic (AFM) ordering in EuAuSb at TN=3.3 K. This transition is further confirmed by heat capacity and electrical resistivity data. The isothermal magnetization data saturate at low magnetic field of μ₀Hₛᶜ=2.9 and μ₀Hₛᵃᵇ=3.8 T for H⊥c and H∥c, respectively, while the magnetization along H⊥c displays a metamagnetic transition around μ₀Hₘᵃᵇ=0.95 T. The electrical resistivity exhibits a metallic behavior down to 35 K; after that it shows an upturn until TN due to the influence of short-range interactions. The longitudinal and transverse magnetoresistances of EuAuSb are negative (~-45% and -42% in 10 T at 2 K, respectively); in the high field at T≤40 K, they switch to a positive value above 40 K. Further, we observe a humplike anomaly in the Hall resistivity [ρxy(H)] data below TN, which is most likely a manifestation of the topological Hall effect. Our two-band model analysis of ρxy(H) data indicates both hole and electron charge carriers contribute to the electrical transport of the compound. The electronic band structure calculations reveal a Γ-centered nodal line in the absence of spin-orbit coupling (SOC). In the presence of SOC, the compound hosts the Dirac point. The Z₂ invariants, in the presence of effective time-reversal and inversion symmetries, categorize this system as a nontrivial topological material. Our combined experimental and theoretical studies suggest EuAuSb to be a potential AFM topological semimetal.