We present a study on the structural, spectroscopic, conducting, and magnetic properties of ${\mathrm{Mg}}_5{\mathrm{C}}_{60}$, which is a two-dimensional (2D) fulleride polymer. The polymer phase is stable up to the exceptionally high temperature of $823\mathrm{K}$. The infrared and Raman studies suggest the formation of single bonds between the fulleride ions and possibly $\mathrm{Mg}\text{−}{\mathrm{C}}_{60}$ covalent bonds. ${\mathrm{Mg}}_5{\mathrm{C}}_{60}$ 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 $200\mathrm{K}$ is attributed to Anderson localization driven by structural disorder.

• Received 25 January 2008

DOI:https://doi.org/10.1103/PhysRevB.77.155431