By means of a specific heat ($C$) and electrical resistivity ($\varrho$) study, we give evidence of a pronounced Fermi liquid (FL) behavior with sizable mass renormalization, $m^{ \ast}/m = 30$, up to unusually high temperatures $\sim$70 K in the layered system Cu$_{ 2/3}$V$_{ 1/3}$V$_2$S$_4$. At low temperature, a marked upturn of both $C$ and $\varrho$ is suppressed by magnetic field, which suggests a picture of Kondo coupling between conduction electrons in the VS$_2$ layers and impurity spins of the V$^{ 3+}$ ions located between layers. This picture opens the possibility of controlling electronic correlations and the FL to non-FL crossover in simple layered materials. For instance, we envisage that the coupling between layers provided by the impurity spins may realize a two-channel Kondo state.
Categories: cond-mat.str-el