Electrical resistivity of solid and liquid Pt: Insight into electrical resistivity of ε-Fe

Knowledge of the transport properties of Fe and its alloys at extreme pressure (P) and temperature (T) conditions are essential for understanding the generation and sustainability of the magnetic field of the rocky planets with a metallic core. Since Pt, an unfilled d-band late transition metal with an electronic structure of Xe4f¹⁴5d⁹6s¹, is paramagnetic and close-packed structure at ambient and high P–T conditions, it is expected that its transport properties at these conditions would be similar to those of ε-Fe. We investigated the T-dependent electrical resistivity of solid and liquid Pt up to 8 GPa and found it constant along its melting curve on the liquid side in agreement with theoretical investigations and experimental results estimated from thermal conductivity measurements. Our results suggest that the T-dependent resistivity of ε-Fe could be linear and would not saturate at high P,T conditions. This, in turn, suggests that the thermal conductivity of liquid Fe at Earth's core conditions may not be as high as previously suggested by models employing saturation resistivity. Hence, thermal convection could have powered the geodynamo before the birth of the inner core. The electrical resistivity and thermal conductivity on the liquid and solid sides of the inner core boundary of the Earth could be different in values.