  The metastable phase of an yttrium sesquicarbide compound, which was vary
recently reported as a new superconductive phase with a Tc value of 18 K, was
prepared under high pressure from the nominal composition of Y2C3 and
Y2C2.9B0.1 in order to investigate this phase. We have succeeded in
reproduction, and in the transport measurement for this 18-K phase. It is
considered that the reason for the higher Tc value than the 11.5 K reported
previously is not the small amount of B as the impurity element from the BN
crucible. The Bc2 value at 0 K estimated from the resistivity data for the 18-K
phase seems to be over 30 T. It means that the Tc and Bc2 values of the 18-K
phase are as high as those of the general A15 compounds.
