Vortices with Fractional Flux in Two-Gap Superconductors and in Extended Faddeev Model

We discuss linear topological defects allowed in two-gap superconductors and equivalent extended Faddeev model. We show that, in these systems, there exist vortices which carry an arbitrary fraction of magnetic flux quantum. Besides that, we discuss topological defects which do not carry magnetic flux and describe features of ordinary one-magnetic-flux-quantum vortices in the two-gap system. The results could be relevant for the newly discovered two-band superconductor ${\mathrm{M}\mathrm{g}\mathrm{B}}_2$.