  We bosonize certain components of level $\ell$ $U_q(\hat{sl}_2)$-intertwiners
of $(\ell + 1)$-dimensions. For $\ell = 2$, these intertwiners, after certain
modification by bosonic vertex operators, are added to the algebra
$U_q(\hat{sl}_2)$ at level 2 to construct all irreducible highest weight
representations of level 1 for the quantum affine algebra $U_q(\hat{sp}_4)$.
