A unified description of gravitation and electromagnetism interacting with Dirac spinors is reconsidered in terms of a non-riemannian 5-dimensional geometry with a one-parameter isometry group. The geometry is generated from a 5-form action principle that is invariant under SO(1,4) induced gauge transformation in the bundle of orthonormal 5-frames. The action includes a generalized Brans-Dicke field and the symmetric choice of frames includes a Jordan-Thiry field. These fields enable the effects of local chirality rotations to induce new interactions in 4 dimensions. A complete solution for the 5-dimensional torsion and SO(1,4) connection is used to construct the reduced action. This is compared with the 5-dimensional variational field equations.