Curved 11D Supergeometry

We examine the theta-expansion of the eleven-dimensional supervielbein. We outline a systematic procedure which can be iterated to any order. We give explicit expressions for the vielbein and three-form potential components up to order ${\cal O}(\th^5)$. Furthermore we show that at each order in the number of supergravity fields, in a perturbative expansion around flat space, it is possible to obtain exact expressions to all orders in theta. We give the explicit expression at linear order in the number of fields and we show how the procedure can be iterated to any desired order. As a byproduct we obtain the complete linear coupling of the supermembrane to the background supergravity fields, covariantly in component form. We discuss the implications of our results for M(atrix) theory.