Full set of superconducting parameters of K3C60

The superconducting parameters are the key for building or identifying the theory responsible for the mechanism of superconductivity. Such parameters for fulleride superconductors have not been well established despite the tremendous efforts over the past 30 years. Here we provide a full set of parameters through a systematic study on a well-characterized K3C60 sample. The obtained high upper critical field of 33.0 +/- 0.5 T from the direct electrical transport measurements together with the relatively high critical temperature and large critical current density classifies K3C60 as a promising three-dimensional superconducting magnet material with the advantage of the rich carbon abundance on the Earth. The evaluation of all self-consistently obtained parameters suggests the unconventional nature of the superconductivity for K3C60 with the joint contributions from the electron-phonon coupling and electron correlations. These results and findings are important not only for fundamentally understanding the superconductivity in fullerides but also for future superconducting magnet developments and applications.