The Bannai-Ito polynomials as Racah coefficients of the sl₋₁(2) algebra

The Bannai-Ito polynomials are shown to arise as Racah coefficients for sl_{-1}(2). This Hopf algebra has four generators including an involution and is defined with both commutation and anticommutation relations. It is also equivalent to the parabosonic oscillator algebra. The coproduct is used to show that the Bannai-Ito algebra acts as the hidden symmetry algebra of the Racah problem for sl_{-1}(2). The Racah coefficients are recovered from a related Leonard pair.