High-resolution OPO spectroscopy of Si2C3 at 5 μm: Observation of hot band transitions associated with ν3

► Si2C3 is a molecule of fundamental importance to structural- and astrochemistry. ► Si2C3 was observed using an optical parametric oscillator operating at 5 μm. ► We detected a weak hot band associated with the strong ν3 fundamental. ► The assignment of this new band is based on high-level coupled-cluster calculations.