  The effect of hydrostatic pressure (P) up to 17 kbar on the superconducting
transition temperature (Tc) of the newly discovered intermetallic non-oxide
perovskite superconductor MgCxNi3 has been reported. The TC is found to
increase with increasing P at a rate of dTc/dP ~ 0.0134 to 0.0155 K/kbar
depending on the value of carbon content x. The absolute value of dTc/dP for
MgCxNi3 is about the same as that of intermetallic RNi2B2C (R = rare earths)
and metallic superconductors but about one order of magnitude smaller than that
of the most recently and intensively studied superconductor MgB2. However, the
dlnTc/dP ~ 0.00181 to 0.00224 kbar-1 and the rate of change of Tc with unit
cell volume (V), dlnTC/dlnV ~ -3.18 to -2.58 of MgCxNi3 are having the
comparable magnitude to that of MgB2 with opposite sign. The increase of Tc
with P in MgCxNi3 can be explained in the frame work of density of states (DOS)
effect.
