Some anomalous properties of the YbxY1-xInCu4 alloy system

We report on lattice parameter, dc and ac susceptibility, thermopower, and resistivity measurements of the Yb x Y 1 - x 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 Yb + 3 and Yb + 2 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 YInCu 4 matrix. The valence transition is detected for x>0.85 by thermopower as well as by susceptibility and resistivity data.