Temperature dependent Mössbauer spectroscopy on 57Fe doped (1 at % of Ni) RNi2B2C and RNiBC provided clear evidence of a pair-breaking field at the Ni site for non-superconducting compounds. This field is not present in the superconducting collinear AF DyNi2B2C, however it appears when this compound is diluted with non-magnetic Lu (Dy1-xLu xNi2B2C). Important local information on the spin structure of the R magnetic moments is obtained for both systems. The local symmetries of RNi2B2C and RNiBC compounds, measured through the deltaE Q, were found to be linearly correlated with the c<FONT FACE=Symbol>¢/</FONT>a ratio (c´ is the distance of the R-C layers between which the Ni2-B2 layers are sandwiched). A scaling of Tc with the local symmetry (c<FONT FACE=Symbol>¢/</FONT>a) was found to be the same for all the RNi2B2C and RNiBC (except for Y) compounds.

X-ray diffraction, ac susceptibility and 57Fe Mössbauer spectroscopy measurements have been performed in the MgC(Ni1-xFe x )(0 <= x <= 0.5) series. The superconducting transition temperature Tc of the undoped sample, determined by ac susceptibility, is <FONT FACE=Symbol>~</FONT> 7K. The Fe doping quickly depresses Tc, completely destroying the superconducting state for x <FONT FACE=Symbol>~</FONT> 0.04. The establishment of an ordered magnetic state is only observed for Fe concentration (x > or = 0.3) far above the concentration for which the superconducting state has completely disappeared. An expansion of the lattice with the increase of the Fe content was observed.