  In this work, the concentration and temperature dependences of the
superconducting gap of the HTSC cuprate in the orthorhombic phase are obtained
within the framework of the Hubbard model taking into account the exchange
mechanism of pairing. The enhanced s*-wave component of the superconducting gap
against the background of the prevailing d-wave component in a narrow range of
hole concentrations in the overdoped region is found. To elucidate the reasons
for such unusual behavior the electronic structure of the low-energy
excitations and the structure of the contributions of the pair states to the
superconducting gap in momentum space were investigated at different doping. It
is shown that the presence of a shallow pocket in the region of the maximum
value of the s*-wave component of the gap results in different symmetry of the
superconducting gap in different regions of the k-space and an increase in the
s*-wave component.
