A method of constructing healthy derivative interactions between multiple massive vectors fields is described. Ghosts are avoided via the same totally antisymmetric structure which protects massive gravity and the Galileon. These interactions are not gauge invariant, but do respect an internal rotational symmetry. By considering non-minimal couplings of these fields to gravity, cosmological applications are discussed for three distinct cases: (i) only temporal components, (ii) only spatial components, (iii) all components, but with special restriction which ensures isotropy.

Previous work has considered these derivative interactions for a single Proca field, and cosmological models corrsponding to cases (i) and (ii). The general method described here for multiple fields, and the new case (iii) which emerges, open up an unexplored class of isotropic cosmologies, with potentially interesting properties.