Optical study of heavy-fermion behavior in U(Pt1-x, Pdx)3

We performed an optical study of the low-energy (down to 1 meV) and low-temperature (down to 5 K) properties of single crystals of U(Pt0.95, Pd0.05)3 and of U(Pt0.9, Pd0.1)3 and we compared the results with those previously obtained on pure UPt3. The low-temperature spectra of U(Pt0.95, Pd0.05)3 show a low-energy (a few meV) structure, very similar to the one observed in UPt3. On the contrary, no structures have been observed in the case of U(Pt0.9, Pd0.1)3, where the spectra exhibit normal metallic behavior. The observed structures are therefore strongly connected with the heavy-fermion properties which are still present in the antiferromagnetic phase of the sample having x=0.05 and disappear as the periodicity (and the coherence) is perturbed by more extensive substitution of Pt with Pd. (orig.)