s+d pairing in orthorhombic phase of copper-oxides

A microscopical theory of electronic spectrum and superconductivity is formulated within the two-dimensional anisotropic t-J model with t_{x}\neq t_{y} and J_{x}\neq J_{y}. Renormalization of electronic spectrum and superconductivity mediated by spin-fluctuations are investigated within the Eliashberg equation in the weak coupling approximation. The gap function has d+s symmetry with the extended s-wave component being proportional to the asymmetry t_{y} - t_{x}. Some experimental consequences of the obtained results are discussed.