Electronic Journal of Differential Equations, Vol. 2020 (2020), No. 49, pp. 1-14. Title: Supercooled Stefan problem with a Neumann type boundary condition Author: Adriana C. Briozzo (CONICET, Rosario, Argentina) Abstract: We consider a supercooled one-dimensional Stefan problem with a Neumann boundary condition and a variable thermal diffusivity. We establish a necessary and sufficient condition for the heat flux at the fixed face x=0, in order to obtain existence and uniqueness of a similarity type solution. Moreover we over-specified the fixed face x=0 by a Dirichlet boundary condition aiming at the simultaneous determination of one or two thermal coefficients. Submitted January 9, 2020. Published May 22, 2020. Math Subject Classifications: 35R35, 80A22, 35K55. Key Words: Stefan problem; supercooling; non-linear thermal diffusivity; similarity solution; determination of thermal coefficient.