We compute the partition function of the trigonometric SOS model with one
reflecting end and domain wall type boundary conditions. We show that in this
case, instead of a sum of determinants obtained by Rosengren for the SOS model
on a square lattice without reflection, the partition function can be
represented as a single Izergin determinant. This result is crucial for the
study of the Bethe vectors of the spin chains with non-diagonal boundary terms.Comment: 13 pages, improved versio