A long lasting controversy on the nature of the reaction between liquid, Al and Al45Cr7 has been ended by planar front solidification experiments of Al-Cr alloy in a Bridgman furnace. Cr depletion in the liquid ahead of the quenched planar interface proves without any ambiguity that the invariant reaction on the Al-rich side of the Al-Cr phase diagram is peritectic. A value of the diffusion coefficient of Cr in liquid Al, D-l = 2.4 x 10(-9) m(2)/s, was also deduced from the solute composition profile measured in the quenched liquid. (C) 2014 Elsevier B.V. All rights reserved.