  The $p_{\rm T}$-differential production cross sections of prompt D$^{0}$,
$\Lambda_{\rm c}^{+}$, and $\Sigma_{\rm c}^{0,++}(2455)$ charmed hadrons are
measured at midrapidity ($|y| < 0.5$) in pp collisions at $\sqrt{s} = 13$ TeV.
This is the first measurement of $\Sigma_{\rm c}^{0,++}$ production in hadronic
collisions. Assuming the same production yield for the three $\Sigma_{\rm
c}^{0,+,++}$ isospin states, the baryon-to-meson cross section ratios
$\Sigma_{\rm c}^{0,+,++}/{\rm D}^{0}$ and $\Lambda_{\rm c}^{+}/{\rm D}^{0}$ are
calculated in the transverse momentum ($p_{\rm T}$) intervals $2 < p_{\rm T} <
12$ GeV/$c$ and $1 < p_{\rm T} < 24$ GeV/$c$. Values significantly larger than
in e$^{+}$e$^{-}$ collisions are observed, indicating for the first time that
baryon enhancement in hadronic collisions also extends to the $\Sigma_{\rm c}$.
The feed-down contribution to $\Lambda_{\rm c}^{+}$ production from
$\Sigma_{\rm c}^{0,+,++}$ is also reported and is found to be larger than in
e$^{+}$e$^{-}$ collisions. The data are compared with predictions from event
generators and other phenomenological models, providing a sensitive test of the
different charm-hadronisation mechanisms implemented in the models.
