  The nature of absorption-selected galaxies and their connection to the
general galaxy population have been open issues for more than three decades,
with little information available on their gas properties. Here we show, using
detections of carbon monoxide (CO) emission with the Atacama Large
Millimeter/submillimeter Array (ALMA), that five of seven high-metallicity,
absorption-selected galaxies at intermediate redshifts, $z \approx 0.5-0.8$,
have large molecular gas masses, $M_{\rm Mol} \approx (0.6 - 8.2) \times
10^{10} \: {\rm M}_\odot$ and high molecular gas fractions ($f_{\rm Mol} \equiv
\: M_{\rm Mol}/(M_\ast + M_{\rm Mol}) \approx 0.29-0.87)$. Their modest star
formation rates (SFRs), $\approx (0.3-9.5) \: {\rm M}_\odot$ yr$^{-1}$, then
imply long gas depletion timescales, $\approx (3 - 120)$ Gyr. The
high-metallicity absorption-selected galaxies at $z \approx 0.5-0.8$ appear
distinct from populations of star-forming galaxies at both $z \approx 1.3-2.5$,
during the peak of star formation activity in the Universe, and lower
redshifts, $z \lesssim 0.05$. Their relatively low SFRs, despite the large
molecular gas reservoirs, may indicate a transition in the nature of star
formation at intermediate redshifts, $z \approx 0.7$.
