  We consider a Dirac fermion in a metric-axial-tensor (MAT) background. By
regulating it with Pauli-Villars fields we analyze and compute its full anomaly
structure. Appropriate limits of the MAT background allows to recover the
anomalies of Dirac and Weyl fermions in the usual curved spacetime, obtaining
in particular the trace anomaly of a chiral fermion, which has been the object
of recent analyses.
