Fig. 1: Thermal conductivity at high pressure and room temperature.

The thermal conductivity of powder Fe (black squares) is comparable with that of single-crystal Fe (black stars) and much larger than that of powder Fe0.96Si0.04 (blue symbols) and Fe0.85Si0.15 (red circles), indicating the strong alloying effect of silicon on the thermal conductivity of Fe. Each set of data includes several runs of measurement with solid symbols for compression and open symbols for decompression cycle, respectively. The measurement uncertainties are ≈10% before 30 GPa, ≈20% at 60 GPa, and ≈25% at 120 GPa. The drastic decrease in the thermal conductivity of Fe around 13 GPa results from the bcc–hcp structural transition30.