  A new first order action for type IIB Dirichlet 3-brane is proposed. Its form
is inspired by the superfield equations of motion obtained recently from the
generalized action principle. The action involves auxiliary symmetric spin
tensor fields. It seems promising for a reformulation of the generalized action
in a structure most adequate for investigating the extrinsic geometry of the
super-3- brane, but also for further studies of string dualities.
