[2] More recent tests have been able to conclusively prove that the substance has an even higher melting point of 3,958 °C exceeding those of tantalum carbide and tantalum hafnium carbide which were both previously estimated to be higher.

[6] Experimental evidence gathered in 2020 confirmed that it did indeed have a higher melting point exceeding 4,000 °C,[7] with more recent ab initio molecular dynamics calculations predicting the HfC0.75N0.22 phase to have a melting point as high as 4,110 ± 62 °C, highest known for any material.

[8] Hafnium carbide is usually carbon deficient and therefore its composition is often expressed as HfCx (x = 0.5 to 1.0).

[2] The magnetic properties of HfCx change from paramagnetic for x ≤ 0.8 to diamagnetic at larger x.

An inverse behavior (dia-paramagnetic transition with increasing x) is observed for TaCx, despite its having the same crystal structure as HfCx.