  We study a longstanding problem of identification of the fermion-monopole
symmetries. We show that the integrals of motion of the system generate a
nonlinear classical Z_2-graded Poisson, or quantum super- algebra, which may be
treated as a nonlinear generalization of the $osp(2|2)\oplus su(2)$. In the
nonlinear superalgebra, the shifted square of the full angular momentum plays
the role of the central charge. Its square root is the even osp(2|2) spin
generating the u(1) rotations of the supercharges. Classically, the central
charge's square root has an odd counterpart whose quantum analog is, in fact,
the same osp(2|2) spin operator. As an odd integral, the osp(2|2) spin
generates a nonlinear supersymmetry of De Jonghe, Macfarlane, Peeters and van
Holten, and may be identified as a grading operator of the nonlinear
superconformal algebra.
