Dielectric anomalies in monoclinic TlInS2 polytypes

—Comparison of room-temperature x-ray diffraction data and temperature-dependent (190–220 K) permittivity data for different polytypes of monoclinic TlInS2 demonstrates that the anomalies in ε(T) at the phase transition correlate with the c cell parameter of the polytypes. The ε(T) curve of single-phase crystals with c ≃ 15 Å shows a single, sharp peak at about 205 K. The peaks in the ε of the polytypes with c ≃ 30 and 60 Å occur at other temperatures, indicating that permittivity data near the phase transition can be used to identify the polytypes present in TlInS2 crystals.