A continuous 37-year record of the geomagnetic field from Argentine Islands Geomagnetic Observatory at Faraday research station (65 ¿S, 64 ¿W), Antarctica, has been analysed to reveal a 27-month periodicity in the amplitude of the semidiurnal Sq variation in the H-component significant at the 98% level. This indicates the presence of a periodicity in the strength of the semidiurnal tide at dynamo region altitudes matching that of the quasi-biennial oscillation (QBO) classically observed in the zonal stratospheric winds at equatorial latitudes. It adds to similar observations (Olsen, 1994) which demonstrated such an effect in the diurnal Sq range at near-equatorial latitudes but which showed no evidence for its presence at mid-latitudes. Faraday research station is in a uniquely advantageous geophysical location for such geographically high-latitude observations. ¿ American Geophysical Union 1996