  Palatini variational principle is implemented on a five dimensional quadratic
curvature gravity model, rendering two sets of equations which can be
interpreted as the field equations and the stress-energy tensor. Unification of
gravity with electromagnetism and the scalar dilaton field is achieved through
the Kaluza-Klein dimensional reduction mechanism. The reduced curvature
invariant, field equations and the stress-energy tensor in four dimensional
spacetime are obtained. The structure of the interactions among the constituent
fields is exhibited in detail. It is shown that the Lorentz force naturally
emerges from the reduced field equations and the equations of the standard
Kaluza-Klein theory is demonstrated to be intrinsically contained in this
model.
