A new material has been made to behave in two distinct ways, helping to break down a significant barrier for understanding the mechanisms of high temperature superconductivity. Known high temperature superconductors fall into two different classes — layered cuprates and iron arsenides. The undoped, parent compounds of the cuprates are insulating, while the parent compounds of iron arsenide superconductors are metallic. Undoped barium–manganese–arsenic (BaMn2As2) has the same crystal structure as BaFe2As2, an iron arsenide superconductor parent compound, but it is a semiconductor and becomes an insulator at low temperatures. Surprisingly, BaMn2As2 becomes metallic rather than superconducting when doped with potassium. The Mn atoms have local magnetic moments in both the undoped and doped material just like the copper in the cuprates. This new material shows that there is a relationship between layered cuprates and arsenides that may be exploited for testing theories of high temperature superconductivity.
Ba<sub>1-x</sub>K<sub>x</sub>Mn<sub>2</sub>As<sub>2</sub>: An Antiferromagnetic Local-Moment Metal