We present the site-charge distribution in the charge-ordered and metallic states of ␣-͑BEDT-TTF͒ 2 I 3 , based on the assignment of the C v C stretching modes 2 , 3 , and 27 of ␣-͑BEDT-TTF͒ 2 I 3 with the aid of 13 C-and deuterium-substituted compounds. The nonuniform site charges in both the metallic and insulating phases were consistent with those determined by a recent x-ray diffraction study. Comparing the line shapes of the chargesensitive vibrational modes of ␣-͑BEDT-TTF͒ 2 I 3 with those of isostructural ␣-͑BEDT-TTF͒ 2 NH 4 Hg͑SCN͒ 4 , we propose a thermally activated fluctuation of charge order in the metallic phase of ␣-͑BEDT-TTF͒ 2 I 3. This fluctuation was considerably suppressed above 0.65 GPa. The optical conductivity in the metallic phase shows no Drude response.

Sodium−hydrogen−C60 ternary compounds have been prepared by intercalation of sodium hydride (NaH) into C60. This method afforded a high-quality superconducting (SC) sample with a large volume fraction, but on the other hand, only a few high-quality SC samples were obtained and most of the samples were nonsuperconducting. However, we have succeeded in transforming a non-SC sample into an SC sample and in enhancing superconductivity. The Rietveld analysis clarifies that the non-SC phase (α-phase) has an orthorhombic structure, in contrast to a cubic structure for the SC phase (β-phase). The absence of superconductivity in the α-phase will be understood by the broken symmetry.

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The crystal structures of tetrakis(alkylthio)tetrathiafulvalene (TTCn–TTF) with long alkyl chains (7 ≤ n ≤ 11) can be divided into two different groups (Form I and Form II) according to the difference in the arrangement of the alkyl chains. Although the crystals of TTC7–TTF exhibit two phases (triclinic and monoclinic), the stacking manner of these phases is nearly the same, Form II. TTC9–TTF crystallizes in two different forms: Form I (the triclinic phase) and Form II (the monoclinic phase). The TTC11–TTF crystal only adopts the Form I structure. Although the molecules in both forms have chair-like shapes and columnar structures, the alkyl chains in the Form I crystals are arranged parallel to each other, resulting in more strongly fastened packing than in the case of the Form II crystals. These results are associated with changes in the electrical resistivities and activation energies of TTCn–TTF over the range of large n.