Structural selectivity behavior of helium in perovskite-group <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>KNbO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>

We investigate the permittivity of helium (He) in perovskite-group ${\mathrm{KNbO}}_{3}$ and its high-pressure polymorphs using Raman scattering. Samples were loaded into either an argon (Ar) or He pressure medium to fingerprint the incorporation of He. Specifically, our high-pressure in situ Raman spectroscopy experiments reveal that He has permeated into the high-pressure tetragonal and cubic perovskite phases, while the ambient orthorhombic phase can hold little He. In contrast, Ar is impermeable into ${\mathrm{KNbO}}_{3}$ under pressure and the results are consistent with previous studies. We further validate the incorporation of He into the lattice sites of ${\mathrm{KNbO}}_{3}$ by using both the disorder effect and Fano resonance analyses. The structural selectivity behavior of He suggests that minerals could potentially induce He concentration heterogeneity within Earth's interior.