WEAKLY SCREENED COULOMB INTERACTION AND PROPERTIES OF HTSCS

In order to explain the anisotropy of the energy gap observed in direct photoemission experiments on the basis of the ''extended saddle-point singularities'' in the electron-energy spectrum lying close to the Fermi level, the assumption is made that the Coulomb interactions are weakly screened, i.e. the Debye screening radius is much larger than the lattice period; this makes the electron interaction anisotropic. Another consequence of this assumption is that at low temperatures the normal-state resistivity is mostly defined by electron-electron scattering. and its temperature dependence is rho is-proportional-to T. Some aspects of the model are discussed.