Short-range antiferromagnetic correlations in Kondo insulators

We study the influence of short range antiferromagnetic correlations betwee n local f-electrons on the transport and thermodynamic properties of Kondo insulators. We use a Kondo lattice model with an additional Heisenberg inte raction between nearest neighboring f-moments, as first proposed by Coqblin et al. [1] for metallic heavy fermions. The inter-site magnetic correlatio ns produce an effective bandwidth for the f-electrons. They are treated on the same footing as the local Kondo correlations such that two energy scale s appear in our approach. We discuss the competition between these two scal es on the physical properties. (C) 2000 Published by Elsevier Science B.V. All rights reserved.