Alterations in the thermodynamic parameters pressure and temperature give rise to the creation of new types of compounds that are not accessible under ambient conditions. In recent years, methodological advances in laser-heated diamond anvil cells combined with multi-grain single-crystal X-ray diffraction have led to the discovery of a large amount of novel carbonitrides, which not only exhibit exclusive structures but also possess physicochemical properties of significant interest. In talk study, I will describe and discuss the discovery of a novel hafnium carbonitride with a unique crystal structure, which is demonstrated to remain stable below 10 GPa upon decompression.