Adding Another Syngony to the K–Cd–Sb System: Synthesis, Structure, and Properties of Cubic, Clathrate-Like K 3 Cd 12 Sb 10

K3Cd12Sb10 was discovered using an unconventional hydride synthetic route, whereas the temperature conditions were rationalized from in situ powder X-ray diffraction. K3Cd12Sb10 can be synthesized in the single-phase form through the hydride method at relatively low temperatures (723 K). K3Cd12Sb10 melts incongruently at 794 K and has a narrow synthesizability window (691–794 K), as determined by in situ high-temperature diffraction and differential scanning calorimetry. Because of its limited thermal stability, suitable crystals for single-crystal X-ray diffraction are unavailable; the crystal structure of K3Cd12Sb10 was solved from high-resolution synchrotron powder X-ray diffraction data. K3Cd12Sb10 crystallizes in a new structure type (space group Ia3̅d, a = 18.09301(1) Å, V = 5922.87(1) Å3, Z = 8), adding another syngony for the previously reported ternary K–Cd–Sb compounds. By merging unconventional synthesis with in situ high-temperature monitoring, this study pushes the boundaries of materials discovery, revealing a clathrate-like phase with a novel structure type and hinting at vast structural diversity across other antimonide systems.