An exceptional geometry for d=11 supergravity?

We analyse the algebraic constraints of the generalized vielbein in S O(1, 2) x S O(16) invariant d = 11 supergravity, and show that the bosonic degre es of freedom of d = 11 supergravity, which become the physical ones upon r eduction to d = 3, can be assembled into an E-8(8)-valued vielbein already in 11 dimensions. A crucial role in the construction is played by the maxim al nilpotent commuting subalgebra of E-8(8), of dimension 36, suggesting a partial unification of general coordinate and tensor gauge transformations.