  We give a realization of the level zero fundamental weight representation
$W(\varpi_k)$ of the quantum affine algebra $U_q'(\mf{g})$, when $\mf{g}$ has a
maximal parabolic subalgebra of type $C_n$. We define a semisimple $U'_q({\mf
g})$-module structure on $\E^{\otimes 2}$ in terms of q-deformed Clifford
generators, where $\E$ is the exterior algebra generated by a dual natural
representation $V$ of $U_q(\mf{sl}_{n})$. We show that each $W(\varpi_k)$
appears as an irreducible summand (not necessarily multiplicity free) in
$\E^{\otimes 2}$. As a byproduct, we obtain a simple description of the affine
crystal structure of $W(\varpi_k)$ in terms of $n\times 2$ binary matrices and
their $(\mf{sl}_n,\mf{sl}_2)$-bicrystal structure.
