1616 supergravity coupled to matter: The low energy limit of the superstring

We analyze irreducible, N = 1 supergravity theories with 16 fermionic degrees of freedom. The lagrangians for pure $\text{16}\text{16}$ supergravity, and for $\text{16}\text{16}$ supergravity coupled to arbitrary chiral superfields are constructed. These theories are shown to have natural SU(1,1) non-compact symmetry. The low energy field theory limit of the superstring is conjectured to be of this type.