Strong coupling between magnetic order and band topology in the antiferromagnet EuMnSb 2

We report a comprehensive magnetization and magnetotransport study on a metallic-type of ${\mathrm{EuMnSb}}_{2}$ single crystals. A large Hall signal up to room temperature is found in our metallic ${\mathrm{EuMnSb}}_{2}$, which is dominated by hole carriers with very low carrier density and high mobility. Clear Shubnikov--de Haas oscillations are observed at low temperatures (T $l$ 30 K), from which a dominant tiny hole pocket with small effective mass is deduced. The interplay of carrier density and Mn and Eu moments results in complex magnetic ground states with two successive antiferromagnetic (AFM) transitions appearing at ${T}_{N1}=24 \mathrm{K}$ and ${T}_{N2}=9 \mathrm{K}$. In line with the rich magnetic phases, the transport properties, including magnetoresistance, quantum oscillation, and Berry phase, experience abrupt disturbances when crossing the magnetic phase boundaries. The Dirac state is likely quenched once the AFM orders set in, indicating a strong coupling between the AFM magnetic order and the band topology. Our results suggest that metallic-type ${\mathrm{EuMnSb}}_{2}$ is an ideal platform for the study of the interplay between magnetism, charge transport, and band topology.