Strong Electronic Correlations in YMn$_{2}$Ge$_{2}$

Exotic phases, like superconductivity, often emerge near electron delocalization transitions in strongly interacting systems. Magnetization, heat capacity and resistivity measurements were performed on single crystals of the antiferromagnetic metal YMn$_{2}$Ge$_{2}$, which is isostructural to the ThCr$_{2}$Si$_{2}$-type iron pnictides. Above the antiferromagnetic ordering temperature T$_{N}$=425 K, the magnetic susceptibility displays Curie-Weiss like behaviour with a fluctuating moment $\mu$ = 3.3 $\mu_{B}$/Mn atom, larger than the ordered moment of 2.2 $\mu_{B}$/Mn atom. Heat capacity measurements yield a Sommerfeld coefficient $\gamma$ = $\frac{C}{T}$ = 8.5 mJ/mol Mn K$^{2}$, nearly three times larger than $\gamma_{Ru}$ = 3.3 mJ/mol Mn K$^{2}$ for its non-magnetic isostructual analog YRu$_{2}$Ge$_{2}$, indicating strong electronic correlations in YMn$_{2}$Ge$_{2}$. The quasiparticle mass enhancement $\frac{m*}{m_{Ru}}$ = $\frac{\gamma}{\gamma_{Ru}}$ = 2.6 is similar to the value observed in the 122-type iron pinctides. Fermi-liquid behaviour of the resistivity $\rho = \rho_{0} + A T^{2}$ is observed over a very broad range of temperatures between 0.5 K and 300 K, with the resistivity at low temperature $\rho$(0.5 K) = 8 $\mu\Omega$ cm indicating high sample quality