Organometallic lanthanide complexes of Ln(n)(C8H8)(m) (Ln = lanthanide metals of Ce, Nd, Eu, Ho, and Yb; C8H8 = 1,3,5,7-cyclooctatetraene) were produced by a combination of laser vaporization and molecular beam methods. The complexes having (n, m) = (n, n + 1) for it 1-5 were prominently produced as magic numbers in the mass spectra. Using mass spectrometry, photoionization spectroscopy, and photoelectron spectroscopy, it is concluded that these magic-numbered complexes form multiple decker sandwich structures in which Ln atoms and C8H8 molecules are alternately piled up. The obtained spectroscopic data show that these sandwich complexes are formed through ionic bonds and are charge transfer complexes, where the Ln atoms are multiply-charged cations of Ln(k+) (k = 2 and 3) and C8H8 molecules are multiply charged anions.