Thermal conductivity \lambda and electrical resistivity \rho of monocrystalline LaSn₃ were measured in temperature range 6--300 K. A high and sharp maximum was observed for \lambda (T) dependence at temperature T_m = 14 K. The dependence has revealed the linear behavior of \lambda with temperature below T_m and the exponential one for temperatures higher than T_m. The electronic component to the thermal conductivity was estimated assuming validity of the Wiedeman--Franz law. It was found that the electrons play an essential role in the heat transport of LaSn₃. Temperature dependence of the Lorenz function for LaSn₃ is given as well.

PACS numbers: 72.15.--v, 72.15.Eb, 72.15.Qm