  We present a study on the structural, spectroscopic, conducting and magnetic
properties of Mg5C60, a two dimensional (2D) fulleride polymer. The polymer
phase is stable up to the exceptionally high temperature of 823 K. Infrared and
Raman studies suggest the formation of single bonds between fulleride ions and
possibly Mg - C60 covalent bonds. Mg5C60 is a metal at ambient temperature as
shown by electron spin resonance and microwave conductivity measurements. The
smooth transition from a metallic to a paramagnetic insulator state below 200 K
is attributed to Anderson localization driven by structural disorder.
