  We construct a two-dimensional topological sigma model whose target space is
endowed with a Poisson algebra for differential forms. The model consists of an
equal number of bosonic and fermionic fields of worldsheet form degrees zero
and one. The action is built using exterior products and derivatives, without
any reference to any worldsheet metric, and is of the covariant Hamiltonian
form. The equations of motion define a universally Cartan integrable system. In
addition to gauge symmetries, the model has one rigid nilpotent supersymmetry
corresponding to the target space de Rham operator. The rigid and local
symmetries of the action, respectively, are equivalent to the Poisson bracket
being compatible with the de Rham operator and obeying graded Jacobi
identities. We propose that perturbative quantization of the model yields a
covariantized differential star product algebra of Kontsevich type. We comment
on the resemblance to the topological A model.
