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Abstract A new compound NaCd₄Sb₃(Rm,a=4.7013(1) Å,c=35.325(1), Å, Z=3,T=100 K) featuring the RbCd₄As₃structure type has been discovered in the Na−Cd−Sb system, in addition to the previously reported NaCdSb phase. NaCd₄Sb₃and NaCdSb were herein synthesized using sodium hydride as the source of sodium. The hydride method allows for targeted sample composition, improved precursor mixing, and an overall quicker synthesis time when compared to traditional methods using Na metal as a precursor. The NaCd₄Sb₃structure was determined from single‐crystal X‐ray diffraction and contained the splitting of a Cd site not seen in previous isostructural phases. NaCd₄Sb₃decomposes into NaCdSb plus melt at 766 K, as determined viain‐situhigh‐temperature PXRD. The electronic structure calculations predict the NaCd₄Sb₃phase to be semi‐metallic, which compliments the measured thermoelectric property data, indicative of ap‐type semi‐metallic material. The crystal structure, elemental analysis, thermal properties, and electronic structure are herein discussed in further detail. 

Abstract The compositional screening of K‐Zn‐Sb ternary system aided by machine learning, rapid exploratory synthesis using KH salt‐like precursor and in situ powder X‐ray diffraction yielded a novel clathrate type XI K₅₈Zn₁₂₂Sb₂₀₇. This clathrate consists of a 3D Zn‐Sb framework hosting K⁺ions inside polyhedral cages, some of which are reminiscent of known clathrate types while others are unique to this structure type. The complex non‐centrosymmetric structure in the tetragonal space groupwas solved by means of single crystal X‐ray diffraction as a 6‐component twin due to pseudocubic symmetry and further confirmed by high‐resolution synchrotron powder X‐ray diffraction and state‐of‐the‐art scanning transmission electron microscopy. The electron‐precise composition of this clathrate yields narrow‐gapp‐type semiconductor with extraordinarily low thermal conductivity due to displacement or “rattling” of K cations inside oversized cages and as well as to twinning, stacking faults and antiphase boundary defects.