The big attraction of the theory exposed here lies in its unifying structure and the high-level (but allowed) overdetermination of the field variables. I was able to show that the field equations yield in first-order approximation equations that correspond to the Newton-Poisson theory of Gravitation and to Maxwell's theory of the electromagnetic field. Nevertheless I'm still far away from claiming the physical validity of the equations I derived. The reason for that is, that I did not succeed in deriving equations of motion for particles yet.