  $YbInCu_{4}$ and its alloys present discontinuous, first order iso-structural
transitions at pressure dependent temperatures $T_V(P)$, where a local moment
phase coexist with a renormalized Fermi liquid phase. We show that along the
coexistence line $T_V(P)$ the entropy of the large volume renormalized Fermi
liquid phase is smaller than that of the higher density, local moment phase.
This implies the existence of a Pomeranchuk effect in these Kondo lattice
materials in analogy with $^3He$. The theoretical possibility of using these
systems as cooling machines is discussed.
