Multiband superconductivity in YNi2B2C single crystals studied by use of specific-heat measurements

We present new specific-heat data for two different YNi2B2C single crystals grown by a zone-melting method. The two samples (Tc,A=15.26(4) K, Tc,B=15.6(1) K) were studied in magnetic fields up to B=9 T in the temperature range from T=0.35..20 K, using both a relaxation and a heat-pulse method. In the superconducting state (B=0) we find an uncommon dependence of the electronic contribution to the specific heat, Cel(T), strengthening the assumption of a multiband nature of the superconducting state of YNi2B2C. A quantitative analysis of Cel(T) evidences multiple electronic contributions from electrons with very different electron-phonon coupling strengths, thus exhibiting several different superconducting energy gaps Δ(T,B=0). This feature is in agreement with recent de Haas-van Alphen results.