We consider recently studied boro-carbides RE(Ni 1− x M x ) 2B 2C, with emphasis in RE=Y and Ho. Ho compounds exhibit in some cases spiral magnetic order. We extended a recent previous work on Heusler compounds to study the specific heat of Y boro-carbides doped with Co and to calculate the coupling between Ho moments in neighbouring planes. The effect of impurity disorder is included in the electronic structure via the Coherent Potential Approximation (CPA) and in the absence of experimental data for the pseudoquaternary specific heat, we restricted ourselves to the dilute limit and determine the impurity potential via Friedel's sum rule. The electron–phonon coupling ( λ( x)) is extracted from the measured superconducting transition temperature, using the Allen–Dines formula. The existent specific heat data for Y compounds is used to fix the parameters of the two sub-lattice model. Finally we study the change, with transition metal concentration, of the angle between moments of the spiral magnetic order.