Hole Doping and Antiferromagnetic Correlations above the N{e}el temperature of the Topological Semimetal (Sr$_{1-x}$K$_x$)MnSb$_2$

Neutron diffraction and magnetic susceptibility studies of orthorhombic single crystal {Ksub} confirm the three dimensional (3D) C-type antiferromagnetic (AFM) ordering of the Mn$^{2+}$ moments at $T_{rm N}=305 pm 3$ K which is slightly higher than that of the parent SrMnSb$_2$ with $T_{rm N}=297 pm 3$ K. Susceptibility measurements of the K-doped and parent crystals above $T_{rm N}$ are characteristic of 2D AFM systems. This is consistent with high temperature neutron diffraction of the parent compound that display persisting 2D AFM correlations well above $T_{rm N}$ to at least $sim 560$ K with no evidence of a ferromagnetic phase. Analysis of the de Haas van Alphen magnetic oscillations of the K-doped crystal is consistent with hole doping.