Mg5C60: A stable two dimensional conducting polymer
  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. 
D. Quintavalle, F. Borondics, G. Klupp, A. Baserga, F. Simon, A.   Janossy, K. Kamaras, S. Pekker