  On the basis of coupled Ginzburg--Landau equations we study nonhomogeneous
states in systems with two order parameters~(OP). Superconductors with
superconducting OP~$\Delta$, and charge- or spin-density wave (CDW or SDW) with
amplitude~$W$ are examples of such systems. When one of OP, say~$\Delta$, has a
form of a topological defect, like, e.g., vortex or domain wall between the
domains with the phases~$0$ and~$\pi$, the other OP~$W$ is determined by the
Gross--Pitaevskii equation and is localized at the center of the defect. We
consider in detail the domain wall defect for~$\Delta$ and show that the shape
of the associated solution for~$W$ depends on temperature and doping (or on the
curvature of the Fermi surface)~$\mu$. It turns out that, provided temperature
or doping level are close to some discrete values~$T_{n}$ and~$\mu_{n}$, the
spacial dependence of the function~$W(x)$ is determined by the form of the
eigenfunctions of the linearized Gross--Pitaevskii equation. The spacial
dependence of~$W_{0}$ corresponding to the ground state has the form of a
soliton, while other possible solutions~$W_{n}(x)$ have nodes. Inverse
situation~when~$W(x)$ has the form of a topological defect and~$\Delta(x)$ is
localized at the center of this defect is also possible. In particular, we
predict a surface or interfacial superconductivity in a system where a
superconductor is in contact with a material that suppresses~$W$. This
superconductivity should have rather unusual temperature dependence existing
only in certain intervals of temperature. Possible experimental realizations of
such non-homogeneous states of OPs are discussed.
