On-shell consistency of the Rarita-Schwinger field formulation
  We prove that any bilinear coupling of a massive spin-3/2 field can be brought into a gauge invariant form suggested by Pascalutsa by means of a non-linear field redefinition. The corresponding field transformation is given explicitly in a closed form and the implications for chiral effective field theory with explicit Delta (1232) isobar degrees of freedom are discussed. 
H. Krebs, E. Epelbaum, U.-G. Mei{\ss}ner