DC AND AC RESISTIVITY OF AMORPHOUS UCU4-X THIN-FILMS(XAL8)

Thin films of the heavy-fermion system UCu4+xAl8-x have been prepared and characterized by x-ray diffraction and by microprobe analysis. The films were found to be in an amorphous state and were subsequently in vestigated by ac-resistivity techniques for frequencies 20 less-than-o r-equal-to nu less-than-or-equal-to 10(9) Hz and temperatures 0.1 less -than-or-equal-to T less-than-or-equal-to 300 K. From these measuremen ts it was concluded that compared to the results in the crystalline bu lk material, the onset of magnetic order is suppressed at low Cu conce ntrations x, while the onset of a coherent heavy-fermion state is supp ressed at high x. All samples investigated reveal a single-ion Kondo b ehavior down to the lowest temperatures. Significant deviations from t he behavior of dipolar Kondo systems were detected. Up to the highest frequencies no indications of a narrow Drude peak could be found.