Bulk quantum Hall effect in eta-Mo4O11

We have observed a quantum Hall effect in the bulk quasi-two-dimensional co nductor eta-Mo4O11 The Hall resistance exhibits well defined plateaux, coin cident with pronounced minima in the diagonal resistance. We present data f or several different samples and contact geometries, and discuss a possible mechanism for the quantum Hall effect in this system. We also discuss the implications of these findings in the light of recent predictions concernin g chiral metallic surface states in bulk quantum Hall systems.