  In this study pseudoquaternary rare-earth nickel borocarbide superconductors
RxR'1-xNi2B2C have been investigated predominantly in the diluted limit x << 1
or (1 x) << 1. In all of these materials structural disorder results in a
reduction of the superconducting transition temperature Tc . Depending on the
selection of the rare earth elements R and R' this disorder induced
deterioration of superconductivity is combined with magnetic pair breaking of
Abrikosov-Gorkov type or pair breaking of non-magnetic impurities in
antiferromagnetic superconductors (Morozov-type of pair breaking).
