  Polycrystalline samples with nominal composition of Ba(Fe1-xIrx)2As2 (x=0.10,
0.15, and 0.20) were investigated by means of X-ray diffraction (XRD), scanning
electron microscopy (SEM), electrical resistivity, and magnetization
measurements. XRD and SEM results showed that almost single phase samples were
obtained. Bulk superconductivity with TC~28 K was observed in the x=0.10
sample. TC~28 K is the highest superconducting critical temperature among the
reported data for electron-doped AFe2As2-type (A=Ca, Sr, and Ba)
superconductors. The upper critical field Hc2(0) reaches as high as 65 T for
the x=0.10 sample. The underlying physics is discussed in connection with
Co-doping case.
