Temperature dependence of the Kondo resonance inYbAl3

We report the observation of a strong temperature dependence of the Kondo resonance in the valence-band photoemission spectrum and of the 3d→4f white line in the x-ray absorption spectrum of ${\mathrm{YbAl}}_3$. The asymmetric Kondo resonance has a binding energy of ∼35 meV with a ∼50 meV width. The temperature dependence of the Yb 4f spectral features and valence are well reproduced by Anderson impurity model calculations with a Kondo temperature of ${\mathit{T}}_{\mathit{K}}$≊400 K, demonstrating that both spectroscopic and near ground state properties can be described within a unified theoretical framework.