The thermoelectric properties (resistivity and thermopower) of single crystals of the low dimensional pentatelluride materials,HfTe5 andZrTe5,have been measured as a function of temperature from 10K<T<320K. The effect of small amounts of Ti substitutional doping(M1−xTixTe5,whereM=Hf, Zr) on the thermoelectric properties is reported here. A resistive transition occurs in the pentatellurides, as evidenced by a peak in the resistivity,TP≈80K forHfTe5andTP≈145K forZrTe5.Both parent materials exhibit a large positive (p-type) thermopower near room temperature which undergoes a change to negative (n-type) below the peak temperature. The thermal conductivity is relatively low (≈5 W/m K) for theMTe5materials. The Ti substitution affects the electronic properties strongly, producing a substantial shift in the peak temperature while the large values of thermopower remain essentially unaffected. These results warrant further investigation of these materials as candidates for low temperature thermoelectric applications. ©1998 American Institute of Physics.