  OsB_2 crystallizes in an orthorhombic structure (Pmmn) which contains
alternate boron and osmium layers stacked along the c-axis. The boron layers
consist of puckered hexagons as opposed to the flat graphite-like boron layers
in MgB_2. OsB_2 is reported to become superconducting below 2.1 K. We report
results of the dynamic and static magnetic susceptibility, electrical
resistivity, Hall effect, heat capacity and penetration depth measurements on
arc-melted polycrystalline samples of OsB_2 to characterize its superconducting
and normal state properties. These measurements confirmed that OsB_2 becomes a
bulk superconductor below T_ c = 2.1 K. Our results indicate that OsB_2 is a
moderate-coupling Type-II superconductor with an electron-phonon coupling
constant \lambda_{ep} \approx 0.4 to 0.5, a small Ginzburg-Landau parameter
\kappa \sim 1 to 2 and an upper critical magnetic field H_{c2}(0.5 K) \sim 420
Oe for an unannealed sample and H_{c2}(1 K) \sim 330 Oe for an annealed sample.
The temperature dependence of the superfluid density n_{s}(T) for the
unannealed sample is consistent with an s-wave superconductor with a slightly
enhanced zero temperature gap \Delta(0) = 1.9 k_{B}T_c and a zero temperature
London penetration depth \lambda(0) = 0.38(2) \mu m. The n_{s}(T) data for the
annealed sample shows deviations from the predictions of the single-band s-wave
BCS model. The magnetic, transport and thermal properties in the normal state
of isostructural and isoelectronic RuB_2, which is reported to become
superconducting below 1.6 K, are also reported.
