Resistivity and magnetic susceptibility of single-crystal Lu(Ni1-xCox)2B2C (x=0.0-0.09)

Single crystal samples of Lu(Ni1-xCox)(2)B2C have been prepared for x=0-0.09. In-plane electrical resistivity measurements show that the residual resistivity of these samples increases linearly with x, though by less than is observed for polycrystalline samples. T-c is suppressed by the cobalt substitution (from 16.0 K for x = 0 to 9.5 K for x = 0.09), though magnetization measurements indicate that this is not due to pair breaking by magnetic impurities. The critical field H-C2(T) decreases with increasing Co concentration, and has some anisotropy between H parallel to c and H perpendicular to c. The ratio of the coherence length to the mean-free path (xi(0)/l) is estimated, and found to be approaching the dirty limit (xi(0)/l much greater than 1) as x increases. These results are discussed with reference to nonlocal effects and the vortex lattice structure of the borocarbides in the mixed state.