  Advances in theoretical calculations boosted the searches for high
temperature superconductors, such as sulfur hydrides and rare-earth
polyhydrides. However, the required extremely high pressures for stabilizing
these superconductors handicapped further implementations. Based upon thorough
structural searches, we identified series of unprecedented superconducting
technetium-borides at moderate pressures, including TcB (P6$_3$/mmc) with
superconducting transition temperature $T_{\text{c}}$ = 20.2 K at ambient
pressure and TcB$_2$ (P6/mmm) with $T_{\text{c}}$ = 23.1 K at 20 GPa.
Superconductivity in these technetium-borides mainly originates from the
coupling between the low frequency vibrations of technetium-atoms and the
dominant technetium-4d electrons at the Fermi level. Our works therefore
present a fresh group in the family of superconducting borides, whose
diversified crystal structures suggest rich possibilities in discovery of other
superconducting transition-metal-borides.
