Noncentrosymmetric (NCS) tetrel pnictides have recently generated interest as nonlinear optical (NLO) materials due to their second harmonic generation (SHG) activity and large laser damage threshold (LDT). Herein nonmetal-rich silicon phosphides RuSi
4P
4 and IrSi
3P
3 are synthesized and characterized. Their crystal structures are reinvestigated using single crystal X-ray diffraction and
29Si and
31P magic angle spinning NMR. In agreement with previous report RuSi
4P
4 crystallizes in NCS space group
P1, while IrSi
3P
3 is found to crystallize in NCS space group
Cm, in contrast with the previously reported space group
C2. A combination of DFT calculations and diffuse reflectance measurements reveals RuSi
4P
4 and IrSi
3P
3 to be wide bandgap (
Eg) semiconductors,
Eg = 1.9 and 1.8 eV, respectively. RuSi
4P
4 and IrSi
3P
3 outperform the current state-of-the-art infrared SHG material, AgGaS
2, both in SHG activity and laser inducer damage threshold. Due to the combination of high thermal stabilities (up to 1373 K), wide bandgaps (≈2 eV), NCS crystal structures, strong SHG responses, and large LDT values, RuSi
4P
4 and IrSi
3P
3 are promising candidates for longer wavelength NLO materials.
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