D=6 massive spinning particle
  The massive spinning particle in six-dimensional Minkowski space is described as a mechanical system with the configuration space ${\ R}% ^{5,1}\times {\ CP}^3$. The action functional of the model is unambigiously determined by the requirement of identical (off-shell) conservation for the phase-space counterparts of three Casimir operators of Poincar\'e group. The model is shown to be exactly solvable. Canonical quantization of the model leads to the equations on wave functions which prove to be equivalent to the relativistic wave equations for the irreducible $6d$ fields. 
S. L. Lyakhovich, A. A. Sharapov and K. M. Shekhter