DO THE A4C60 FULLERIDES HAVE A BROKEN-SYMMETRY GROUND-STATE

Band theory predicts both K3C60 and K4C60 to be metals; various experi mental probes show that while K3C60 is indeed metallic, K4C60 appears to be insulating. The standard view of this apparent failure of the si ngle-particle picture is that electron correlation is predominant. We describe an alternative scenario, motivated on theoretical grounds, wh ich invokes a spin- or charge-density-wave state to explain the observ ed insulating behavior.