High T<SUB>c</SUB> copper-oxide superconductors of thallium, bismuth and lead

A brief survey of compositions and structures of high-temperature copper oxide superconductors containing thallium, bismuth and lead is presented. All these compounds possess CuO2 sheets but not Cu[sbnd]O chains. Another structural feature common to all these compounds is that the part of the structure between nonconsecutive CuO2 sheets is ill-defined. Possible correlations of Tc with the structure and bonding of these compounds are pointed out