High-temperature superconductivity has a range of applications from sensors to energy distribution. Recent reports of this phenomenon in compounds containing electronically active BiS2 layers have the potential to open a new chapter in the field of superconductivity. Here we report the identification and basic properties of two new ternary Bi-O-S compounds, Bi2OS2 and Bi3O2S3. The former is non-superconducting; the latter likely explains the superconductivity at T(c) = 4.5 K previously reported in "Bi4O4S3". The superconductivity of Bi3O2S3 is found to be sensitive to the number of Bi2OS2-like stacking faults; fewer faults correlate with increases in the Meissner shielding fractions and T(c). Elucidation of the electronic consequences of these stacking faults may be key to the understanding of electronic conductivity and superconductivity which occurs in a nominally valence-precise compound.

We report the structures and physical properties of two new iridates, NaIrO 3 and Sr 3 CaIr 2 O 9 , both of which contain continuous two-dimensional honeycomb connectivity. NaIrO 3 is produced by room temperature oxidative deintercalation of sodium from Na 2 IrO 3 , and contains edge-sharing IrO 6 octahedra that form a planar honeycomb lattice. Sr 3 CaIr 2 O 9 , produced via conventional solid-state synthesis, hosts a buckled honeycomb lattice with novel corner-sharing connectivity between IrO 6 octahedra. Both of these new compounds are comprised of Ir 5+ (5d 4 ) and exhibit negligible magnetic susceptibility. They are thus platforms to investigate the origin of the nonmagnetic behavior exhibited by Ir 5+ oxides, and provide the first examples of a J = 0 state on a honeycomb lattice.

We report the discovery of surface states in the perovskite superconductor [Tl4]TlTe3 (Tl5Te3) and its nonsuperconducting tin-doped derivative [Tl4](Tl0.4Sn0.6)Te3 as observed by angle-resolved photoemission spectroscopy. Density functional theory calculations predict that the surface states are protected by a Z2 topology of the bulk band structure. Specific heat and magnetization measurements show that Tl5Te3 has a superconducting volume fraction in excess of 95%. Thus Tl5Te3 is an ideal material in which to study the interplay of bulk band topology and superconductivity.