Electrical resistance of the most refractory carbide $\rm Ta_{0.8}\rm Hf_{0.2}\rm C$ in the solid and liquid states $(2000$–$5000$ K$)$

Carbide $\rm Ta_{0.8}\rm Hf_{0.2}\rm C$ in the form of a thin magnetron sputtering layer $(\sim 1\,\mu$m$)$ was studied under rapid heating $(5\,\mu$s$)$ by an electric current pulse. The resistivity of this carbide (referred to initial dimensions) and temperature coefficient of resistance were obtained up to $5000$ K for the first time. The temperature was measured by surface radiation with the help of high-speed pyrometer calibrated by a temperature tungsten lamp. The sharp rise of temperature coefficient of resistance before melting indicates an increase in the concentration of defects before melting. This confirms the assumption of the appearance of non-stationary paired Frenkel defects in the lattice of rapidly heated solids, which does not have time to establish the equilibrium concentration of vacancies in the lattice.