By analysis of the electronic contribution to the binding in A3C60, the authors show that the problem of orientational ordering can be mapped onto the FCC nearest-neighbor antiferromagnetic Ising model with J at the order of 100 K. For T<1.76 J, the system should be found in a state which is antiferromagnetically ordered in two dimensions and disordered in the third. This is not inconsistent with present X-ray powder data. The authors find that the low-temperature conduction-band structure closely resembles that of the simplest antiferromagnetically ordered (so-called bidirectional) crystal.
 

Physical Review Letters, 70 4142-5, 1993.