The Raman and IR-absorption spectra of the Cs 2Te 4O 12 lattice are first recorded and interpreted. Extraordinary features observed in the structure and Raman spectra of Cs 2Te 4O 12 are analyzed by using ab initio and lattice-dynamical model calculations. This compound is specified as a caesium-tellurium tellurate Cs 2Te IV(Te VIO 4) 3 in which Te IV atoms transfer their 5 p electrons to [Te VIO 4] 3 6− tellurate anions, thus fulfilling (jointly with Cs atoms) the role of cations. The Te VI–O–Te VI bridge vibration Raman intensity is found abnormally weak, which is reproduced by model treatment including the Cs + ion polarizability properties in consideration.