K_3+δC₈₄. Higher fullerene analogues of the A₃C₆₀ superconductors

Face-centered cubic phases of both the D₂ and D_2d isomers of the C₈₄ anion with band fillings close to those of the A₃C₆₀ superconductors are prepared by a two-step reaction involving saturated K_8+χC₈₄ phases as intermediates. Rietveld refinement shows that the structures are more disordered than those of K_8+χC₈₄, with incomplete occupancy of multiple cation sites and the presence of two anion orientations, while both temperature-dependent powder diffraction and EPR demonstrate the monophasic nature of the reaction products. The temperature-independent magnetic susceptibilities and line width variation in EPR indicate that these phases have finite densities of states at the Fermi level for both C₈₄ majority isomers, unlike the previously prepared saturated phases, but dc magnetization measurements indicate the absence of superconductivity above 5 K.