  We report the first detection of SiC$_2$ in the interstellar medium. The
molecule was identified through six rotational transitions toward
G\,+0.693$-$0.027, a molecular cloud located in the Galactic center. The
detection is based on a line survey carried out with the GBT, the Yebes 40m,
and the IRAM 30m telescopes covering a range of frequencies from 12 to 276 GHz.
We fit the observed spectra assuming local thermodynamic equilibrium and derive
a column density of ($1.02\pm0.04)\times10^{13}$ cm$^{-2}$, which gives a
fractional abundance of $7.5\times10^{-11}$ with respect to H$_2$, and an
excitation temperature of $5.9\pm0.2$ K. We conclude that SiC$_2$ can be formed
in the shocked gas by a reaction between the sputtered atomic silicon and
C$_2$H$_2$, or it can be released directly from the dust grains due to
disruption. We also search for other Si-bearing molecules and detect eight
rotational transitions of SiS and four transitions of Si$^{18}$O. The derived
fractional abundances are $3.9\times10^{-10}$ and $2.1\times10^{-11}$,
respectively. All Si-bearing species toward G\,+0.693$-$0.027 show fractional
abundances well below what is typically found in late-type evolved stars.
