POINT-CONTACT STUDY OF UCU4-X COMPOU NDS(XAL8)

The first derivative dV/dI(V) of the IVC and its temperature dependenc e for heterocontacts between the compounds UCu4+xAl8-x (x = 0; 0.5; 1. 5) and pure metals Cu, Fe, Ni have been measured. It has been found th at main peculiarities of dV/dI(V) appear at a temperature below T whi ch is close to the Neel temperature for the compounds with x = 0 and 0 .5. In this case dV/dI(V) behaviour agrees well with that calculated a ssuming a thermal regime of current flow through the point contact in view of the matter properties degradation at the surface. For a sample with x = 1.5 the T exceeds considerably the temperature of a maximum of resistivity, which is related to the manifestation of coherent eff ects in going to a heavy-fermion state. The possible causes of such di fference are discussed.