Evidence for possible 4fbands atT≫TKin the heavy-fermion single crystalCePt2+x

We report the observation of strong amplitude variations with k in the 4f photoelectron spectra of a nearly trivalent heavy-fermion compound (${\mathrm{CePt}}_{2+\mathit{x}}$). 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≊10${\mathit{T}}_{\mathit{K}}$. Kondo lattice-derived bands are expected to exist only at T≪${\mathit{T}}_{\mathit{K}}$, 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.