  Recent results of A. Sen on quantum field theory models with self-dual field
strengths use string field theory as a starting point. In the present work, we
show that combining string field theory and supergeometry we can provide a
constructive method for all these models, for any superspace representation and
for any given background. The analysis is based on the new concept of
pseudoform, emerging in supergeometry, which opens a new page in quantum field
theory and, in particular, in supergravity. The present work deals with an
explicit example, the case of the chiral boson multiplet in d=2.
