syntectic reaction
A reversible reaction that involves the conversion of two liquid phases, l' and l'', into a solid phase α on cooling: \[\text{l}^{'}+\text{l}^{''}\rightleftharpoons \unicode[Times]{x3B1} \] The maximum temperature at which this reaction can occur is the congruent melting point of the solid phase. Example: The conversion of co-existing K-rich and Zn-rich phases in the K-Zn system to form an intermediate solid phase KZn13.
PAC, 1994, 66, 577. 'Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)' on page 592 (