Anomalous properties of the ${\mathrm{Yb}}_x{\mathrm{Y}}_{1-x}{\mathrm{InCu}}_4$ alloy system

We report on lattice parameter, dc and ac susceptibility, thermopower, and resistivity measurements of the ${\mathrm{Yb}}_x{\mathrm{Y}}_{1-x}{\mathrm{InCu}}_4$ alloy system. With increasing x the system evolves from semimetallic towards more metallic character. Some anomalous properties, such as the concentration dependence of the lattice parameter can be explained as an admixture of ${\mathrm{Yb}}^{+3\mathrm{}}$ and ${\mathrm{Yb}}^{+2\mathrm{}}$ ions. Only for the lowest concentrations of Yb do we observe signs of the Kondo effect with a $T_K$ of about 2 K, which is much lower than expected. The absence of a signature of the Kondo effect in the thermopower data for the lowest concentrations we explain by the semimetallic character of the ${\mathrm{YInCu}}_4$ matrix. The valence transition is detected for $x>\mathrm{}0.85\mathrm{}$ by thermopower as well as by susceptibility and resistivity data.