Specific heat in the mixed state of non-magnetic borocarbides

The temperature and magnetic field dependence of the specific heat cp(T,H) in the superconducting mixed state has been measured for polycrystalline YxLu1-xNi2B2C and Y(Ni1-yPty)2B2C samples. The deviations from the usual linear-in-H law of the linear-in-T electronic specific heat contribution γ(H)T can be possibly ascribed to unconventional pairing. The γ(H) dependence is discussed in the unitary d-wave scenario as well as in the intermediate transition region in between dirty and clean s-wave limits. From a consideration of γ(H) data, unconventional pairing cannot be ruled out. © 2002 Published by Elsevier Science B.V.