Specific heat of the ytterbium monopnictides above 5 K from a band-structure calculation

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Abstract
Applying the self-consistent large-degeneracy expansion to the degenerate Anderson impurity model in the presence of crystal fields, we compute the specific heat of YbN, YbP, and YbAs above 5 K. Each crystal-field level couples to the band states with its own hybridization function, determined from a tight-binding fit to an ab initio band-structure calculation. The different amplitudes of the couplings naturally explain the anomalous crystal-field splittings observed by inelastic neutron scattering. Our calculations reproduce the hitherto unexplained excess specific-heat peak seen in all three compounds around 5 K, which we interpret as being due to the Kondo effect for the ground-state doublet.