Double-degenerate Bose-Fermi mixture of strontium

We report on the attainment of a spin-polarized Fermi sea of Sr-87 in thermal contact with a Bose-Einstein condensate (BEC) of Sr-84. Interisotope collisions thermalize the fermions with the bosons during evaporative cooling. A degeneracy with T/T-F = 0.30(5) is reached for a Sr-87 Fermi sea of 2 x 10(4) atoms together with an almost pure Sr-84 BEC of 10(5) atoms.