Superconductivity in layered YB₂C₂

Superconductivity in the layered yttrium diboride dicarbide, YB2C2, has been revisited by means of specific heat, magnetic susceptibility and resistivity measurements down to 50 mK revealing a bulk superconducting transition at 1.0 K. Analysing the low temperature specific heat we obtain a Sommerfeld coefficient of the normal state electonic contribution, gamma = 3.1(1) mJ/mol K-2, and a Debye temperature, Theta(LT)(D) = 680(10) K. The specific heat anomaly at T-C, Delta C similar or equal to 4.5 mJ/mol K, thus, yields a thermodynamic ratio Delta C/gamma T-C similar or equal to 1.4 in close agreement with the BCS value. For polycrystalline (YB2C2)-B-11 prepared by inductive melting we observe a pronounced resistive anomaly near 3.6K which, however, corresponds to a rather spurious specific heat anomaly and is thus attributed to traces of YC2 present in this sample.