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Physical properties of bco phase of Cs3+αC60 (α=0.0−1.0) and A15 phase of Cs3C60 are studied by X-ray diffraction, ESR, AC susceptibility, resistivity and Raman. The ESR of Cs300(6)C60 showed a broad peak of ∼380 G due to conduction electron, while no broad peak was observed in the ESR of bco Cs3+αC60 (α≠0.0) and A15 phase. This shows that only bco phase of Cs3C60 is metallic. The AC susceptibility of bco phase of Cs3.2(3)C60 and Cs3.5(1)C60 showed no superconducting transition above 1.3 K even under high pressure, and the resistivity was 0.52 Ω cm for both samples.

Temperature dependence of resistivity, ρ, of a two-dimensional polymer phase of Na4C60 has been studied from 190 to 300 K. The ρ was 6.9×103 Ω cm at 300 K, which is higher by six orders than those of metallic fullerides. The temperature dependence of ρ shows a semiconducting behavior in this temperature region. This result is different from the previous result derived from ESR which suggests a metallic property above 100 K. The gap energy, Eg, was estimated to be 0.8 eV. This value is close to those of other A4C60 (A:K, Rb and Cs).

The local lattice instability around the imperfection doped in the host matrix is investigated with ultra-violet absorption spectra and x-ray excitation spectra. The local environment of a cuprous ion in NaCl shrinks, and in NaBr cuprous ion is lacated away from the regular lattice site. This phenomenon is discussed with the pseudo Jahn–Teller effect.

X-ray diffractions of two-dimensional Na4C60 are studied at various temperatures above 11 K in a pressure region up to 67 kbar. All X-ray diffraction patterns measured in this study can be analyzed by using a body-centered monoclinic (bcm) structure of space group I2/m. New Bragg reflections which cannot be assigned to I2/m are not observed in all X-ray diffraction patterns. The β at 11 K and 67 kbar is the smallest (93.66(8)°) among those of Na4C60 lattice of bcm. In this crystal, the center-to-center distance, 9.57(2) A, between the C60 molecules associated with van der Waals contacts approaches to that, 9.20(2) A, between the C60 molecules in a polymer chain, suggesting the realization of three-dimensional polymeric structure in Na4C60 at a higher pressure than 67 kbar.