NONMONOTONOUS EVOLUTION OF THE KONDO TEMPERATURE IN THE PHASE-DIAGRAMOF CE(PD1-XCUX)(2)SI-2

The evolution of the behavior of the Ce 4f electron with the Cu conten t in the alloy Ce(Pd1-xCux)(2)Si-2 was investigated by determining its structural, magnetic, transport, and thermal properties. Results obta ined on 15 samples with compositions distributed along the whole conce ntration range allow us to draw a magnetic phase diagram showing three distinct regions. The first region at low Cu concentrations correspon ds to the antiferromagnetic-ordered regime. The fast suppression of th is magnetic order between x = 0.2 and x = 0.25 suggests the presence o f a critical point which separates this region from the second one at larger.x values where no magnetic order is observed. The main characte ristic of this second region, which extends up to x = 0.7, is a pronou nced increase of the Kondo temperature T-K, from T-K approximate to 15 K at x = 0.25 to T-K approximate to 50 K at x = 0.7. This is in contr ast with the fast decrease of T-K in the region with x > 0.7. In this region a small anomaly with a ferromagnetic character is observed in t he specific hear arround 4 K. The change in the evolution of T-K with x coincides with a change in the composition dependence of the c latti ce parameter of the tetragonal structure, pointing to a structure-rela ted origin of this unusual T-K(x) behavior. This nonmonotonous T-K(x) dependence is reproduced using local-density-approximation band-struct ure calculations, which show a maximum of the hybridization strength b etween conduction electrons and Ce 4f stares for intermediate Cu conce ntrations. Such a T-K(x) dependence which contradicts the monotonous d ependence observed in all other Ce-based alloy systems is the hallmark of the Ce(Pd1-xCux)(2)Si-2 alloy, which cannot be described as a Ferm i-Liquid system in the nonmagnetic region. [S0163-1829(98)02118-3].