It's Elemental - The Element Hafnium
Melting near 3890°C, hafnium carbide (HfC) has the highest melting point of any known two-element compound. Hafnium nitride (HfN) also has a high melting point, around 3305°C. Other hafnium compounds include: hafnium chloride (HfCl 4 ), hafnium fluoride (HfF 4 ) and hafnium oxide (HfO 2 ).