Melting diagrams of Fe-rich alloys determined from synchrotron in situ measurements in the 15-23Â GPa pressure range

We confirm very high solubility of Si and C with solid iron, and report a Si partitioning coefficient of 1.3(2) at 16.9 GPa. The S and O solubility in solid iron appears very small. Therefore, both S and/or O could explain density jumps between liquid outer and solid inner parts of planetary cores, at least up to ∼25 GPa.