EVIDENCE FOR POSSIBLE 4F BANDS AT T-MUCH-GREATER-THAN-T-K IN THE HEAVY-FERMION SINGLE-CRYSTAL CEPT2+X

We report the observation of strong amplitude variations with k in the 4f photoelectron spectra of a nearly trivalent heavy-fermion compound (CePt2+x). The amplitude of the 4f feature, previously identified as the Kondo resonance, displays the full symmetry of the lattice, suggesting some band character already at T10TK. Kondo lattice-derived bands are expected to exist only at TTK, so that this would seem to favor conventional bands at high T. The single-impurity model by contrast demands purely localized behavior at these temperatures. © 1995 The American Physical Society.