  We investigate the role played by particular field representations of an
intermediate massive spin-1 boson in the context of spin-dependent
interparticle potentials between fermionic sources in the limit of low momentum
transfer. The comparison between the well-known case of the Proca field and
that of an exchanged spin-1 boson (with gauge-invariant mass) described by a
2-form potential mixed with a 4-vector gauge field is established in order to
pursue an analysis of spin- as well as velocity-dependent profiles of the
interparticle potentials. We discuss possible applications and derive an upper
bound on the product of vector and pseudo-tensor coupling constants.
