  We present a comparison between the average atomic gas mass, $\langle
M_{Atom}\rangle$ (including HI and He), the average molecular gas mass,
$\langle M_{Mol}\rangle$, and the average stellar mass, $\langle M_*\rangle$,
of a sample of star-forming galaxies at $z\approx0.75-1.45$, to probe the
baryonic composition of galaxies in and during the epoch of peak star-formation
activity in the universe. The $\langle M_{Atom}\rangle$ values of star-forming
galaxies in two stellar-mass matched samples at $z=0.74-1.25$ and
$z=1.25-1.45$, were derived by stacking their HI 21cm signals in the
GMRT-CAT$z1$ survey. We find that the baryonic composition of star-forming
galaxies at $z\gtrsim 1$ is dramatically different from that at $z\approx0$.
For star-forming galaxies with $\langle M_*\rangle\approx10^{10} M_\odot$, the
contribution of stars to the total baryonic mass, $M_{Baryon}$, is
$\approx61\%$ at $z\approx0$, but only $\approx16\%$ at $z\approx1.3$, while
molecular gas constitutes $\approx6\%$ of the baryonic mass at $z\approx0$, and
$\approx14\%$ at $z\approx1.3$. Remarkably, we find that atomic gas makes up
$\approx70\%$ of $M_{Baryon}$ in star-forming galaxies at $z\approx1.3$. We
find that the ratio $\langle M_{Atom}\rangle/\langle M_*\rangle$ is higher both
at $z\approx1.0$ and at $z\approx1.3$ than in the local Universe, with $\langle
M_{Atom}\rangle/\langle M_*\rangle\approx1.4$ at $z\approx1.0$, and
$\approx4.4$ at $z\approx1.3$, compared to its value of $\approx0.5$ today.
Further, we find that the ratio $\langle M_{Atom}\rangle/\langle
M_{Mol}\rangle$ in star-forming galaxies with $\langle M_*\rangle
\approx10^{10} M_\odot$ is $\approx2.3$ at $z\approx1.0$ and $\approx5.0$ at
$z\approx1.3$. Overall, we find that atomic gas is the dominant component of
the baryonic mass of star-forming galaxies at $z\approx1.3$, during the epoch
of peak star-formation activity in the universe.
