ANISOTROPY OF THE SUPERCONDUCTING GAP IN CECO2

We find extraordinary superconducting characteristics in the low-tempe rature specific heat of high quality CeCo2 single crystals, suggesting that the superconducting gap is highly anisotropic. The electronic sp ecific-heat jump at the superconducting transition temperature (T-c=1. 5 K) is Delta C-e/T-gamma(c)=0.85, which is reduced compared to the BC S value of 1.43. At low temperatures (0.13<T/T-c much less than 1), C- e varies approximately as T-2, indicating a possibility of lines of no des in the gap. A possible correlation of the gap anisotropy with the ferromagnetic spin fluctuation is discussed.