On the recently proposed martensitic-like structural transformation in V, Nb, and Ta

A recent announcement [Phys. Rev. Lett. 107, 075503, (2011)], after anomalies in the thermal expansion, of a previously unknown martensitic transformation in pure Nb, Ta and V is discussed in the light of anelastic measurements on Nb samples with comparable purities. It results that the effects of the alleged transformation on the anelastic spectra would be at least three orders of magnitude smaller than in typical martensitic transformations. A possible alternative explanation for the observed anomalies is proposed in terms of precipitation of unnoticed residual H.