  The superconductor MgCNi3 has been chemically doped by partial substitution
of Ru for Ni in the solid solution MgCNi3-xRux for 0<x<0.5. Magnetic and
specific heat measurements show that the Sommerfeld parameter (gamma_exp) and
TC decrease immediately on Ru substitution, but that a TC above 2K is
maintained even for a relatively large decrease in gamma_exp. Ferromagnetism is
not observed to develop through Ru substitution, and the normal state magnetic
susceptibility is suppressed.
