M-theory duality and BPS-extended supergravity

We discuss toroidal compactifications of maximal supergravity coupled to an extended configuration of BPS states which transform consistently under th e U-duality group. Under certain conditions this leads to theories that liv e in more than eleven spacetime dimensions, with maximal supersymmetry but only partial Lorentz invariance. We demonstrate certain features of this co nstruction for the case of nine-dimensional N = 2 supergravity.