[en] An x-ray phase analysis data and measurement of the electric and magnetic properties of R-Ba- Cu-O, Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O samples are reported, where R is yttrium and the whole rare-element series with the exception of Pm. A deviation of the resistivity ρ(T) and magnetic susceptibility χ(T) in the region T_c < t < 1.4T_c from their temperature dependences, as extrapolated above 180 K, is found to be a manifestation of both fluctuation superconductivity and admixed superconducting phases with T_c < 180 K. The correlation between an increase of T_c and the decrease of the mean normalized interplanar distance bar ε = 2c/aq is discussed. The extrapolation of T_c (bar ε) dependences for systems with Bi and Tl gives T_c = 140-10 K at bar ε = 0.95. Although superconducting phases at bar ε < 0.95 must be unstable in these systems at standard conditions they may be formed in alloyed or multiphase samples