  We carry out the strong coupling expansion for the SU(N) Kondo model where
the impurity spin is represented by a L-shaped Young tableau. Using second
order perturbation theory around the strong coupling fixed point it is shown
that when the antisymmetric component of the Young-tableau contains more than
N/2 entries, the strong-coupling fixed point becomes unstable to a two-stage
Kondo effect. By comparing the strong coupling results obtained here with the
result using a supersymmetric large N expansion, we are also able to confirm
the validity of the the supersymmetric formalism for mixed symmetry Kondo
models.
