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Abstract The novel potassium sulfido cobaltate, K2[Co3S4] is introduced, with 25% vacancies of the cobalt positions within a layered anionic sublattice. The impedance and dielectric investigations indicate a remarkable ionic conductivity of 21.4 mS cm−1 at room temperature, which is in the range of highest ever reported values for potassium‐ions, as well as a high electrical permittivity of 2650 at 1 kHz, respectively. Magnetometry results indicate an antiferromagnetic structure with giant intrinsic exchange bias fields of 0.432 and 0.161 T at 3 and 20 K respectively, potentially induced by a combination of the interfacial effect of combined magnetic anionic and nonmagnetic cationic sublattices, as well as partial spin canting. The stability of the exchange bias behavior is confirmed by a training effect of less than 18% upon 10 hysteresis cycles. The semiconductivity of the material is determined, both experimentally and theoretically, with a bandgap energy of 1.68 eV. The findings render this material as a promising candidate for both, active electrode material in potassium‐ion batteries, and for spintronic applications.

Over the decades, intensive explorations have been conducted to understand the nature of d10−d10 interactions. The recent establishment of a bonding indicator named the crystal orbital bond index stimulated our impetus to probe the capabilities of that approach for the examples of Ag–Ag interactions in different tellurides. In the framework of our quantum chemical explorations, we inspected the electronic structures of two tellurides which were previously reported to comprise d10−d10 interactions, while the third candidate material, i.e., RbCe2Ag3Te5, has been obtained from reactions of rubidium chloride, cerium, silver and tellurium for the very first time. The outcome of our explorations clearly shows that the nature of Ag–Ag interactions is well mirrored by the corresponding COBI.