Pomeranchuk effect in unstable Ytterbium systems
  $YbInCu_{4}$ 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. 
Mucio A. Continentino and Andre S. Ferreira