SrMn$_2$Ge$_2$: A metallic system with anomalous magnetotransport properties

Abstract

The structural, electronic, and physical properties of previously unexplored layered tetragonal compound SrMn$_2$Ge$_2$ are reported. The compound crystallizes in the ThCr$_2$Si$_2$-type structure with a crystallographic parameters $c/a$ ratio of $2.535(3)$, significantly smaller than those of the related BaMn$_2$$Pn_2$ compounds ($Pn =$ P, As, Sb, Bi), indicating enhanced interlayer interaction between the moment-bearing Mn-ions. Magnetic susceptibility measurements suggest an antiferromagnetic ground state with a high Neél temperature $T_{\rm N} > 350$~K\@. A large and positive magnetoresistance (MR) of approximately $50\%$ is observed at low temperatures, which follows a power-law field dependence with exponent $n = 1.50(8)$. Low-temperature electrical resistivity data reveal Kondo-like features. Heat capacity measurements show no signs of a phase transition below 300~K and further confirm a metallic ground state. Electronic structure calculations reveal a three-dimensional Fermi surface and suggest the presence of substantial electronic correlation effects.