Comment on: "The Frenkel Line: a direct experimental evidence for the new thermodynamic boundary"

In a recent publication (D. Bolmatov et al. Sci.Rep. 5, 15850 (2015)) the experimental observation of structural transformations on crossing the Frenkel line in supercritical argon is claimed. Here we show that no experimental evidence of the structural transformation was presented. The reported experimental observations which Bolmatov et al. claim as evidence of a transition across the Frenkel line are instead due to the irregularity of the experimental (P,T) path in their work.