Short-range antiferromagnetic correlations in Kondo insulators

We study the influence of short range antiferromagnetic correlations between local f -electrons on the transport and thermodynamic properties of Kondo insulators. We use a Kondo lattice model with an additional Heisenberg interaction between nearest neighboring f-moments, as first proposed by Coqblin et al.[1] for metallic heavy fermions. The inter-site magnetic correlations produce an effective bandwidth for the f -electrons. They are treated on the same footing as the local Kondo correlations such that two energy scales appear in our approach. We discuss the competition between these two scales on the physical properties.