We surprisingly made a new n-type thermoelectric compound NbCoSb with half-Heusler (HH) structure having valence electron count of 19, different from the traditional 18, which opens up a new route to develop new half-Heusler thermoelectric materials not following the traditional valence electron count of 18. The samples are made by arc melting followed by ball milling and hot pressing. The effect of hot pressing temperature on the thermoelectric properties of NbCoSb samples has been studied. A maximum thermoelectric figure-of-merit (ZT) of similar to 0.4 is achieved at 700 degrees C in NbCoSb sample that is hot pressed at 1000 degrees C. This work add a new member to HH compounds for thermoelectric applications, although the peak ZT of similar to 0.4 is still lower than that of the traditional HHs. Moreover, it is very interesting to see that a traditionally thought of valence electron counts of 18 is not required. (C) 2015 Elsevier Ltd. All rights reserved.