  We report the discovery and characterization of two small transiting planets
orbiting the bright M3.0V star TOI-1468 (LSPM J0106+1913), whose transit
signals were detected in the photometric time series in three sectors of the
TESS mission. We confirm the e planetary nature of both of them using precise
radial velocity measurements from the CARMENES and MAROON-X spectrographs, and
supplement them with ground-based transit photometry. A joint analysis of all
these data reveals that the shorter-period planet, TOI-1468 b ($P_{\rm b}$ =
1.88 d), has a planetary mass of $M_{\rm b} = 3.21\pm0.24$ $M_{\oplus}$ and a
radius of $R_{\rm b} =1.280^{+0.038}_{-0.039} R_{\oplus}$, resulting in a
density of $\rho_{\rm b} = 8.39^{+ 1.05}_{- 0.92}$ g cm$^{-3}$, which is
consistent with a mostly rocky composition. For the outer planet, TOI-1468 c
($P_{\rm c} = 15.53$ d), we derive a mass of $M_{\rm c} = 6.64^{+ 0.67}_{-
0.68}$ $M_{\oplus}$, a radius of $R_{\rm c} = 2.06\pm0.04\,R_{\oplus}$, and a
bulk density of $\rho_{c} = 2.00^{+ 0.21}_{- 0.19}$ g cm$^{-3}$, which
corresponds to a rocky core composition with a H/He gas envelope. These planets
are located on opposite sides of the radius valley, making our system an
interesting discovery as there are only a handful of other systems with the
same properties. This discovery can further help determine a more precise
location of the radius valley for small planets around M dwarfs and, therefore,
shed more light on planet formation and evolution scenarios.
