Superconductivity in sodium-hydrogen-C60 ternary compound

The magnetic properties of the superconducting sodium-hydrogen-C 60 ternary compound have been investigated by means of SQUID and ESR. The superconducting parameters (the penetration depth λ and the coherence length ξ) are estimated to be λ=2800 A and ξ=38 A using H c1 (0)= 90 G and H c2 (0)= 22 T. The spin susceptibility and the ESR linewidth decrease sharply below ~250 K, suggesting the presence of some phase transition.