The absence of a metallic phase in magnesium fullerides

Magnesium fullerides MgxC60 ( 1 < x ≤ 6 ) were prepared by a solid-state reaction. Mg3.9C60 was assigned a rhombohedral structure with a = 0.999  nm, α=55.1°. All MgxC60 fullerides were found to have almost the same rhombohedral structure. Mg4.9C60 did not show metallicity based on the electrical resistivity and electron spin resonance measurements. MgxC60 appears to form polymers over a wide range of Mg concentrations and behaves as a non-magnetic insulator.