Conversion Between $$^3$$ 3 He Melting Curve Scales Below 100 mK

We provide the conversion parameters to allow a $$^3$$ He melting curve thermometer to be used to calibrate secondary thermometers to the PLTS2000 temperature scale (Rusby et al. in J Low Temp Phys 149(3):156, 2007). Additional fits to the phase diagram of superfluid $$^3$$ He are also provided using the melting curve P, T measurements and of the phase diagram of superfluid $$^3$$ He (Greywall in Phys Rev B 33(11):7520, https://doi.org/10.1103/PhysRevB.33.7520 , 1986) as a bridge. Further, the melting curve measurements of Osheroff and Yu (Phys Lett A 77(6):458, https://doi.org/10.1016/0375-9601(80)90539-3 , 1980) are also used to extend the scale below 0.9 mK.