we were able to reveal the magnon specific heat contribution of the heavy members of the borocarbides and to identify the expressions that describe their thermal evolution. These expressions (given in terms of only two physically accepted parameters) were derived from the spin-wave analysis of a simple Hamiltonian that consists of effective exchange couplings and anisotropic interactions. We investigated as well an influence of the magnons on the superconductivity of these AF superconductors.

Improvements and extension of this analysis are underway. These include, on the experimental side, probing the magnon contribution in single crystals of $R$Ni$_{2}$B$_{2}$C by other (microscopic and macroscopic) techniques and, on the theoretical side, a better and more realistic approximation of  $J(k)$, CEF effects, and magnetoelastic, and anisotropic exchange forces.

Partial financial support were provided by Brazilian agencies CNPq and FAPERJ.

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