Supplementary Information Synthesis, Crystal Structure and Magnetic Characterization of a Series of Cu II Ln III Heterometallic [Ln = La, Ce, Pr, Nd and Sm) Metal–Organic Compounds with an Unusual Single Crystal to Single Crystal Phase Transition Pau Díaz-Gallifa, Oscar Fabelo, Laura Cañadillas-Delgado, Jorge Pasán, Ana Labrador, Francesc Lloret, Miguel Julve and Catalina Ruiz-Pérez. A B C D E Photograph S1. Detail of the crystal morphology of compounds 1A-5A (A-E).