Supplementary Material

The supplementary material includes additional Raman data for ice XV build-up (Fig. S1), a comparison of Avrami plots based on dielectric and Raman data (Figs. S2 and S3) including kinetic parameters (Tab. S1). Furthermore it shows an example for the Raman superposition analysis to determine fractions of ices (Fig. S4) and heating protocols for dielectric measurements (Fig.S5).