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

Abstract

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 $P{6}_{3}/mmc$. The magnetic measurements reveal an antiferromagnetic (AFM) ordering in EuAuSb at ${\mathit{T}}_{N}=3.3$ K. This transition is further confirmed by heat capacity and electrical resistivity data. The isothermal magnetization data saturate at low magnetic field of ${\ensuremath{\mu}}_{0}{H}_{s}^{c}=2.9$ and ${\ensuremath{\mu}}_{0}{H}_{s}^{ab}=3.8$ T for $\mathit{H}\ensuremath{\perp}\mathit{c}$ and $\mathit{H}\ensuremath{\parallel}\mathit{c}$, respectively, while the magnetization along $\mathit{H}\ensuremath{\perp}\mathit{c}$ displays a metamagnetic transition around ${\ensuremath{\mu}}_{0}{H}_{m}^{ab}=0.95$ T. The electrical resistivity exhibits a metallic behavior down to 35 K; after that it shows an upturn until ${T}_{N}$ due to the influence of short-range interactions. The longitudinal and transverse magnetoresistances of EuAuSb are negative ($\ensuremath{\sim}\ensuremath{-}45%$ and $\ensuremath{-}42%$ in 10 T at 2 K, respectively); in the high field at $\mathit{T}\ensuremath{\le}40$ K, they switch to a positive value above 40 K. Further, we observe a humplike anomaly in the Hall resistivity [${\ensuremath{\rho}}_{xy}(\mathit{H})$] data below ${T}_{N}$, which is most likely a manifestation of the topological Hall effect. Our two-band model analysis of ${\ensuremath{\rho}}_{xy}(\mathit{H})$ data indicates both hole and electron charge carriers contribute to the electrical transport of the compound. The electronic band structure calculations reveal a $\mathrm{\ensuremath{\Gamma}}$-centered nodal line in the absence of spin-orbit coupling (SOC). In the presence of SOC, the compound hosts the Dirac point. The ${Z}_{2}$ 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.