  We propose that the spin-chain with the PSU(2|2)xU(1)^3 symmetry is
equivalent to the non-linear sigma-model on PSU(2|2)xU(1)^3/{HxU(1)} with a
certain subgroup. To this end we show that the spin-variable of the former
theory is identified as the Killing scalar of the latter and their correlation
functions can have the same integrability. It is crucial to think that the
respective theory gets the PSU(2|2)xU(1)^3 symmetry by a symmetry reduction the
exceptional supergroup D(2,1;gamma), rather than by an extension of PSU(2|2).
