The thermal behaviour of 4‐propyl‐4′‐thiocyanatobiphenyl (3TCB) was studied by adiabatic calorimetry. In addition to the isotropic liquid and smectic E (SmE) phases, five crystalline phases were detected. Such a rich polymorphism was not observed for the other low‐n members of the nTCB homologous series (n = 2–5). The observed anomalies are analysed and the possible origin for their existence is suggested. The temperature quench of the SmE phase leads to a metastable crystalline state with a multiple‐stage relaxation process.