ESR under pressure on polymer phase A(1)C(60) (A=Rb, Cs)

Electron spin resonance (ESR) studies under hydrostatic pressure were perfo rmed to investigate the electronic structure of orthorhombic linear polymer phase A(1)C(60) (A=Rb, Cs). Pressure dependence of the antiferromagnetic t ransition temperature and the Curie-Weiss temperature was investigated by t he ESR intensity. On the basis of these data, together with the electrical resistivity on a single crystal under pressure (Phys. Rev. B56, 6627 (1997) ), a Mott-Hubbard phase diagram is proposed for Rb1C60. At ambient pressure this material is suggested to be on the border of the metal-insulator tran sition.