A construction of level 1 irreducible modules for $U_q({\widehat{sp}}_4)$ using level 2 intertwiners for $U_q({\widehat{sl}}_2)$

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