The thermal conductivity of semiclathrate hydrates and aqueous solutions of tetrabutylammonium bromide (TBAB) and tetrabutylammonium chloride (TBAC) was measured for the first time in the temperature range from 223 to 303 K under atmospheric pressure. A transient hot-wire apparatus using a parylene-coated probe was employed for the measurements with an uncertainty of +/- 0.7%. The experimental results indicate that the thermal conductivity of two semiclathrate hydrates are smaller than those of two clathrate hydrates-about 80% of the THF hydrate and 60% of the CH4 hydrate-and are about a factor of 5.5 lower than that of ice Ih at temperatures near the melting point. In addition, the temperature coefficient of the thermal conductivity of semiclathrate hydrate show a weak negative, and the thermal conductivity is more sensitive to the molar mass of a guest molecule. (C) 2015 The Authors. Published by Elsevier B.V.