Nonstandard coproducts and the Izergin-Korepin open spin chain

Corresponding to the Izergin-Korepin (A⁽²⁾₂) R matrix, there are three diagonal solutions ('K matrices') of the boundary Yang-Baxter equation. Using these R and K matrices, one can construct transfer matrices for open integrable quantum spin chains. The transfer matrix corresponding to the identity matrix K = double-struck I sign is known to have U_q(o(3)) symmetry. We argue here that the transfer matrices corresponding to the other two K matrices also have U_q(o(3)) symmetry, but with a nonstandard coproduct. We briefly explore some of the consequences of this symmetry.