Magnetic and Electrical Transport Properties of Dirac Compound BaMnSb$_{\mathrm{2}}$*

BaMnSb$_{\mathrm{2}}$ is a layered compound containing Sb square nets that is theoretically predicted to host Dirac fermions. We have carried out experimental investigations on electrical transport and magnetic properties of BaMnSb$_{\mathrm{2}}$ single crystals. Both in-plane ($\rho _{\mathrm{ab}})$ and c-axis ($\rho_{\mathrm{c}})$ resistivities show metallic behavior with a small bump in $\rho_{\mathrm{c}}$ located near 40 K, while there is large anisotropy $\rho_{\mathrm{c}}$ / $\rho _{\mathrm{ab}}$ (\textasciitilde 100 at 300 K) that increases with decreasing temperature to 1500 at 2 K. Interestingly, Shubnikov-de Hass (SdH) oscillations are observed for both $\rho_{\mathrm{ab}}$ and $\rho _{\mathrm{c}}$ over a wide temperature and magnetic field range. Quantitative analysis indicates that large amplitude SdH oscillations result from nearly massless Dirac Fermions. Furthermore, our magnetic measurements indicate an A-type antiferromagnetic magnetic ordering below 286 K where ferromagnetic ordering is observed in the ab plane with antiferromagnetic coupling along the c direction. These results indicate that BaMnSb$_{\mathrm{2}}$ is a 2D magnetic Dirac material.