Congruent melting point represents a definite temperature just like the melting points of pure components. In some phase diagrams, the congruent melting point of a compound AB may lie above the melting points of pure components A and B. But it is not always necessarily the case. There are different types of systems known in which the congruent melting point is observed below the melting points of the pure components. This happens for inter-metallic compounds, for example, for MgSi 2.