  Harmonic maps from $\BR^2$ or one-connected domain ${\O}\subset \BR^2$ into
$GL(m, \BC)$ and $U(m)$ are treated. The GBDT version of the B\"acklund-Darboux
transformation is applied to the case of the harmonic maps. A new general
formula on the GBDT transformations of the Sym-Tafel immersions is derived. A
class of the harmonic maps similar in certain ways to line-solitons is obtained
explicitly and studied.
