QUASI-ONE-DIMENSIONAL ELECTRONIC-STRUCTURE IN ORTHORHOMBIC RBC60

X-ray diffraction studies show that the stable phase of the alkali ful lerene RbC60 is orthorhombic (o-RbC60) below 350 K. C60 molecules form chains along a with an unusually short spacing of 9.12 angstrom and m agnetic properties suggest that o-RbC60 is a quasi-1 D metal with a tr ansition to a spin density wave ground state at 50 K. The high tempera ture fcc phase of RbC60 may be stabilized below 300 K by quenching fro m 500 K; it is paramagnetic above 300 K and transforms into a nonmagne tic ground state between 300 and 250 K.