  We study f(R)-gravity with torsion in presence of Dirac massive fields. Using
the Bianchi identities, we formulate the conservation laws of the theory and we
check the consistency with the matter field equations. Further, we decompose
the field equations in torsionless and torsional terms: we show that the
non-linearity of the gravitational Lagrangian reduces to the presence of a
scalar field that depends on the spinor field; this additional scalar field
gives rise to an effective stress-energy tensor and plays the role of a scale
factor modifying the normalization of Dirac fields. Problems for fermions
regarding the positivity of energy and the particle-antiparticle duality are
discussed.
