SUSY IN THE SKY

Spinning particles in curved space-time can have fermionic symmetries generated by the square root of bosonic constants of motion other than the hamiltonian. We present a general analysis of the conditions unde r which such new supersymmetries appear, and discuss the Poisson-Dirac algebra of the resulting set of charges, including the conditions of closure of the new algebra. An example of a new non-trivial supersymme try is found in black-hole solutions of the Kerr-Newman type and corre sponds to the Killing-Yano tensor, which plays an important role in so lving the Dirac equation in these black-hole metrics.