WHY SUPPRESSION OF T-C IN LN(1-X)PR(X)BA(2)CU(3)O(7) DEPENDS ON LN

We report the LDA+U-f calculations of the electronic structure of ABa( 2)Cu(3)O(7), (A=Pr, Nd). For A=Pr an additional band crosses the Fermi level, grabbing holes from the (super)conducting CuO2 band. For A=Nd this band remains completely filled, thus explaining the absence of T- c suppression. On doping LnBa(2)Cu(3)O(7) with Pr the position of the hole-depleting band depends crucially of the atomic number of the host rare earth, through the position of its f-band. This makes T-c suppre ssion in doped compounds different for different hosts, the stronger t he smaller the atomic number of the host is.