  The Hall effect can be extended by inducing a temperature gradient in lieu of
electric field that is known as the Nernst (-Ettingshausen) effect. The
recently discovered spin Nernst effect in heavy metals continues to enrich the
picture of Nernst effect-related phenomena. However, the collection would not
be complete without mentioning the valley degree of freedom benchmarked by the
observation of the valley Hall effect. Here we show the experimental evidence
of its missing counterpart, the valley Nernst effect. Using millimeter-sized
WSe$_{2}$ mono-multi-layers and the ferromagnetic resonance-spin pumping
technique, we are able to apply a temperature gradient by off-centering the
sample in the radio frequency cavity and address a single valley through
spin-valley coupling. The combination of a temperature gradient and the valley
polarization leads to the valley Nernst effect in WSe$_{2}$ that we detect
electrically at room temperature. The valley Nernst coefficient is in very good
agreement with the predicted value.
