  We develop a general procedure for the analysis of bulk thermodynamic data of
a superconductor for samples containing a metallic non-superconducting second
phase. The method is based on the condensation energy and it allows the
extraction of the intrinsic properties of a superconductor even for non-ideal
samples. Applying this procedure to the recently discovered geometrically
frustrated beta-pyrochlore superconductor RbOs2O6 (Tc = 6.4 K) yields a
Sommerfeld coefficient as high as 79 mu J/g/K^2 (44 mJ/mol_f.u./K^2). RbOs2O6
is inferred to be a strong type-II superconductor (kappa(Tc) = 23) in the
intermediate-coupling regime similar to niobium (lambda_ep \approx 1). From the
upper critical field mu_0 H_c2 \approx 6 T at 0 K, we estimate a
Ginzburg-Landau coherence length xi \approx 74 AA. The condensation energy is
860 mu J/g (483 mJ/mol_f.u.) resulting in 1/(8 pi) (gamma_1 Tc^2)/DeltaU_1
\approx 0.15, a value well in the range of conventional phonon-mediated
superconductors. The superconducting electronic specific heat indicates
conventional s-wave pairing. The experimental Sommerfeld coefficient of 44
mJ/mol_f.u./K^2 is about 4 times larger than the one found in band structure
calculations. Together with the electron-phonon coupling constant lambda_ep
\approx 1 this leaves an additional lambda_add \approx 2.4 for enhancement due
to other mechanisms.
