The design and discovery of novel functional materials is one of most popular field in modern condensed matter sciences, and the strongly correlated electron systems with intertwined lattice, charge, orbital and spin degrees of freedom continue to attract considerable attention due to their fascinating physical properties. Since these materials tend to have dense and strongly-bonded structures, the application of high-pressure high-temperature synthesis techniques are particular useful to explore and stabilise such metastable phases. With utilising diffraction methods and systematic symmetry analysis, we aim to examine the structure-property relationship and to tailor the desired functionality.