  Extending the formulation for open superstring field theory given in
arXiv:1508.00366, we attempt to construct a complete action for heterotic
string field theory. The action is non-polynomial in the Ramond string field
Psi, and we construct it order by order in Psi. Using a dual formulation in
which the role of eta and Q is exchanged, the action is explicitly obtained at
the quadratic and quartic order in Psi with the gauge transformations.
