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The possibility of fully describing the behavior of transverse resistivity {rho}{sub {ital c}} in cuprate superconductors exclusively in terms of some recently proposed normal-state models is discussed. It is shown that these models do not give a completely satisfactory description of the apparent singularity in {rho}{sub {ital c}} at the critical temperature in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{ital x}}, and that they fail to describe data concerning a lower-{ital T}{sub {ital c}} cuprate superconductor as Bi{sub 2}Sr{sub 2}CuO{sub 6+{ital x}} ({ital T}{sub {ital c}}{approx_equal}15 K). It is argued that these difficulties cannot be overcome considering the normal-state contribution to {rho}{sub {ital c}} only. The role of the density of states fluctuations in the behavior of {rho}{sub {ital c}} just above the transition temperature is recalled. It is shown that, taking into account this contribution, it is possible to dramatically simplify the description of the normal-state transverse resistivity. This can give important hints for the understanding of the transverse electrical transport properties of these materials. {copyright} {ital 1996 The American Physical Society.}

The model for electronic transport in quasicrystals is proposed. Unlike all previous attempts to explain unusual electronic properties of quasicrystals by impending localization due to the lack of periodicity in defectless quasiperiodic lattices, the current theory is focused on phonon and impurity scattering in real, ``dirty'' quasicrystals. The standard scattering theory cannot be applied to quasicrystals, due to their unusual band structure, namely the fact that the Fermi surface is nearly obliterated. To solve the problem a fractional multicomponent Fermi-surface model has been introduced: the Fermi surface has been viewed as consisting of relatively large number of residual tiny electron and hole pockets, with impurity random potential scattering electrons between different components. Leaving quasiperiodicity aside, the Dyson equations for the scattering time, dc conductivity and thermopower have been solved analytically. The theory explains the nearly vanishing conductivity, as well as strong temperature dependence of thermopower and related transport properties. \textcopyright{} 1996 The American Physical Society.

Measurements of the excess conductivity above the transition temperature on selected, high-quality, superconducting epitaxial films of the 2:2:1:2-phase Bi-Sr-Ca-Cu-O (BSCCO), obtained by liquid-phase epitaxy, are reported. The data confirm the two-dimensional nature of the thermodynamical fluctuations in BSCCO compounds in a wide range of temperature above ${\mathit{T}}_{\mathit{c}}$ and very good agreement is found with an extended version of the Aslamazov-Larkin theory [L. Reggiani, R. Vaglio, and A. A. Varlamov, Phys. Rev. B 44, 9541 (1991)].