  The volume change and heat capacity at the ferromagnetic phase transition in
CoS2 were measured at high pressures using X-rays generated by the Argonne
synchrotron light source and by ac-calorimetry, respectively. The transition
entropy, calculated on the basis of these experimental data, drops along the
transition line due to quantum degradation, as required by Nernst law. The
volume change increases strongly along the transition line, which is explained
by specifics of the compressibility difference of coexisting phases that
results from nearly half metallic nature of the ferromagnetic phase of CoS2.
