A new material of higher fullerene, Rb x C 84 , was synthesized by intercalating Rb metal into C 84 crystals. The Rb x C 84 crystals showed a simple cubic ͑sc͒ structure with lattice constant, a, of 16.82͑2͒ Å at 6.5 K, and 16.87͑2͒ Å at 295 K. The Rietveld refinements were achieved with the space group, Pa3, based on a model that the C 2 axis of D 2d -C 84 aligned along ͓111͔. The sample composition was determined to be Rb 8.8͑7͒ C 84 . The ESR spectrum at 303 K was composed of a broad peak with peak-to-peak linewidth ⌬H pp of 220 G, and a narrow peak with ⌬H pp of 24 G. Temperature dependence of the broad peak clearly showed a metallic behavior. The metallic behavior was discussed based on a theoretical calculation. This finding of new metallic phase in a higher fullerene is the first step for a development of new types of fullerene materials with novel physical properties such as superconductivity.

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