Super p-Brane Theories and New Spacetime Superalgebras

We present a geometric formulation of super $p$--brane theories in which the Wess--Zumino term is $(p+1)$--th order in the supersymmetric currents, and hence is manifestly supersymmetric. The currents are constructed using a supergroup manifold corresponding to a generalization of a superalgebra which we found sometime ago. Our results generalize Siegel's analogous reformulation of the Green--Schwarz superstring. The new superalgebras we construct underly the free differential superalgebras introduced by de Azc\'arraga and Townsend a few years ago.