The word of the day is monotectic:
The reversible transition, on cooling, of a liquid to a mixture of a second
liquid and a solid. (IUPAC Compendium on Chemical Terminology)
"An equimolar mixture of dilauroyl phosphatidylcholine and distearoyl phosphatidylcholine, which shows a monotectic behaviour, is hydrolysed at all temperatures."
- J.A.F. Op den Kamp et al., "Action of pancreatic phospholipase A2 on phosphatidylcholinebilayers in different physical states", Biochimica et Biophysica Acta 406:169 (1975).