Pseudogap state in slightly doped by aluminium and praseodymium YBa${}_2$Cu${}_3$O${}_{7-\delta }$ single crystals with a given topology of plane defects

In present work the conductivity in the basis plane of YBaCuO single crystals slightly doped by Al and Pr with a pre-specified topology of twin boundaries has been investigated. The excess conductivity for the analyzed samples shows dependence like $\mathrm{\Delta }\sigma \sim (1-T\mathrm{/}{T}^{\ast })\exp ({\mathrm{\Delta }}_{ab}^{\ast }\mathrm{/}T)$ in wide temperature range $T_f<T<T^{\ast }$, where $T^{\ast }$ can be represents as mean field temperature of superconducting transition. The temperature dependence of pseudogap can be satisfactory described in terms of the BCS-BEC crossover theoretical model.