THEORETICAL INTERPRETATION OF OPTICAL CONDUCTIVITY OF YBCU4AG,AU

We focus on YbCu4Ag and YbCu4Au and interpret the optical conductivity , measured from 2 meV to 6 eV at 10 and 300 K, in terms of self-consis tent electronic structure calculations. Most of the relevant spectral structures are interpreted as interband transitions from hybridized f- d states below and at the Fermi level at high symmetry points. Tn part icular, the large shoulder at about 2.4 and 2 eV in the spectrum of Yb Cu4Au and YbCu4Ag, respectively, can be interpreted in terms of a tran sition Gamma(4) --> Gamma(3) involving mostly d states. We also compar e the electronic structure of YbCu4Ag with that of LuCu4Ag, to ascerta in the influence of the f states on the conduction bands and carrier d ensity at E(F). This allows us to draw some qualitative considerations on the S-band hybridization in these compounds. (C) 1996 American Ins titute of Physics.