  The boride compounds MB_x related to the magnesium-boron stacking layered
material MgB2 are discussed in terms of the B-B layers in the borides analogous
to the Cu-O ones in the cuprates. We propose a possibility of superconducting
materials which exhibit higher critical temperature T_c than 39 K of MgB2. We
point out a role of interstitial ionic atoms M (e.g., Mg in MgB2) as
capacitors, which reduce the condensation-energy loss due to the charging
energy E_c between the B-B layers. In the viewpoint of the present model, the
recently discovered 117-Kelvin superconductor C60/CHBr3 is also discussed in
terms of the intercalation molecules CHBr3 as possible capacitors among the
superconducting grains of C60 molecules.
