  The low-temperature specific heat C(T,H) of a new superconductor MgCNi3 has
been measured in detail. (C/gammasub_nTc=1.97 is estimated from the anomaly at
Tc. At low temperatures, the electronic contribution in the superconducting
state follows Ces/gammasub_nTc=7.96exp(-1.46Tc/T). The magnetic field
dependence of gamma(H) is found to be linear with respect to H. Tc estimated
from the McMillan formula agrees well with the observed value. All the specific
heat data appear to be consistent with each other within the moderate-coupling
BCS context. It is amazing that such a superconductor unstable to
ferromagnetism behaves so conventionally. The Debye temperature Thetasub_D=287
K and the normal state gammasub_n=33.6 mJ/mol K2 are determined for the present
sample. Discussions on the existence of a small magnetic coupling and
unconventional order parameter are also presented.
