  We study the influence of short range antiferromagnetic correlations between
local $f$-electrons on the transport and thermodynamic properties of Kondo
insulators, as first proposed by Coqblin et al. 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.
