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Unusual behaviour of the Kondo temperatures in YbAgxIn1-xCu4

We have found that the temperature of the thermopower minimum of the YbIn1-xAg-xCu4 alloy system (x >= 0.5) shows the same concentration dependence as the Kondo temperature extracted from susceptibility measurements. However, in average these temperatures are about four times smaller than the Kondo temperatures. The resistivity data indicate that the Kondo temperature of the lowest lying ground state level, TKl, increases with x what is an unexpected behavior for the Yb+3 ion since the lattice constant decreases with x. On contrary, the Kondo temperature of the all ground state levels, TKh, decreases with increasing x for x > 0.5. We discuss these unusual experimental facts and suggest possible explanations. In addition we show that the thermopower data of YbIn1-xAgxCu4 clearly demonstrate the effect of coherence on thermopower for x = 1.

YbAgxIn1-xCu4; Kondo temperature

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