Specific heat studies of lanthanum and yttrium sesquicarbides

The specific heats of the sesquicarbides LaC sub(1.35) and La sub(0.9)Th sub(0.1)C sub(1.6) (prepared by arc melting) and YC sub(1.35) (prepared by a high-pressure technique) have been measured for the first time. No bulk specific heat anomaly appears in either lanthanum compound, even though (1) inductively measured super-conducting transition temperatures are respectively high (11.0 K for LaC sub(1.35) and 12.7 K for La sub(0.9)Th sub(0.1)C sub(1.6)) and (2) YC sub(1.35) is a bulk superconductor with a T sub(c) = 10.5 K and Y sub(0.7)Th sub(0.3)C sub(1.58) (also prepared by high pressure) was previously reported to be a bulk superconductor with a T sub(c) = 17.1 K. The apparent correlation with preparation technique is discussed.