Evidence for possible 4f bands at T much-gt TK 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 T∼10TK. Kondo lattice-derived bands are expected to exist only at T much-lt TK, 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