Concentrated kondo effects in PdCe ordering alloys

Changes in the electrical resistivity and Ce valence have been measured as a function of the annealing temperature T_a for Pd-Ce ordering alloys. The absolute value of the resistivity increases and the temperature coefficients decrease significantly with increasing T_a. The anomalies in the resistivity can be explained in terms of an effect of localized 4f electrons in Ce, or the 'concentrated Kondo effect'. The Ce valence and the atomic volume averaged over the alloys show little change with T_a, while the degree of order decreases. These results suggest that there is an inhomogeneity in the spatial distribution of the Ce valence in alloys with a low degree of order, and the inhomogeneity causes the remarkable T_a dependence of the resistivity and the small change in the averaged valence of Ce.