  We found four series of harmonically related lines in IRC\,+10216 with the
Yebes\,40m and IRAM\,30m telescopes. The first series corresponds to a molecule
with a rotational constant, $B$, of 1448.5994$\pm$0.0013 MHz and a distortion
constant, $D$, of 63.45$\pm$1.15 Hz and covers upper quantum numbers from
$J_u$=11 up to 33 (B1449). The second series is fitted with
$B$=1446.9380$\pm$0.0098 MHz and $D$=91$\pm$23 Hz and covers upper quantum
numbers from $J_u$=11 up to 17 (B1447). The third series is fitted with
$B$=598.7495$\pm$0.0011 MHz and D=6.13$\pm$0.43 Hz and covers quantum numbers
from $J_u$=26 up to 41 (B599). Finally, the frequencies of the last series of
lines can be reproduced with $B$=594.3176$\pm$0.0026 MHz and $D$=4.92$\pm$1.16
Hz (B594). The large values of $D$ point toward four metal-bearing carriers.
After exploring all plausible candidates containing Na, Al, Mg, and other
metals, our ab initio calculations indicate that the cations MgC$_4$H$^+$,
MgC$_3$N$^+$, MgC$_6$H$^+$, and MgC$_5$N$^+$ must be the carriers of B1449,
B1447, B599, and B594, respectively. These cations could be formed by the
radiative association of Mg$^+$ with C$_4$H, C$_3$N, C$_6$H, and C$_5$N,
respectively. We calculated the radiative association rate coefficient of
Mg$^+$ with C$_4$H, C$_3$N, C$_6$H, and C$_5$N and incorporated them in our
chemical model. The results confirm that the Mg-bearing cations can be formed
through these radiative association reactions in the outer layers of
IRC\,+10216. This is the first time that cationic metal-bearing species have
been found in space. These results provide a new paradigm on the reactivity of
ionized metals with abundant radicals and open the door for further
characterization of similar species in metal-rich astrophysical environments.
