The aim of the proposal is the preparation and characterization of novel TI based on ternary chalcogenides of Bi, Pb, and Tl. This leads to third generation TI in line with the first (Bi1-xSbx) and second generation TI (Bi2Te3, Bi2Se3, Sb2Te3). As a promising material for topologically protected surface states Bi2Si2Te6 was recently investigated. Like Bi2Te3 it shows a layered crystal structure and a very small direct band gap with inversion of s- and p-states upon spin-orbit-coupling (SOC). It allows for studies of isoelectronic substitution effects by Ge, Sb and Se. Further, compounds of composition A2Rh3S2 are investigated. With the choice of A = Tl, Pb, Bi band structures indicate TI properties that again can be design upon substitution effects.
