An assembly for a gas turbine engine comprising: a case (24, 224) having an inner side defining a portion of a gas path (22, 122) of the gas turbine engine and an outer side opposite the inner side, the case (24, 224) having an aperture extending from the inner side to the outer side; a sealing member; and a vane disposed in the gas path (22, 122) and comprising: a vane body extending through the aperture; and a vane head disposed at an end of the vane body and disposed outside the gas path (22, 122), the vane head having: an abutting surface contacting an outer surface of the case (24, 224); and a groove receiving the sealing member, the groove surrounding an inner region including the aperture when the vane body extends through the aperture, the groove extending completely around an axis of the aperture and opening to the abutting surface, characterised in that: the groove defines a circumferential path around the aperture axis at a peripheral end of the vane head, the groove is outwardly open relative to the inner region and the aperture axis, and the groove has an inner seating surface receiving the sealing member and hindering movement of the sealing member toward the abutting surface, wherein the inner seating surface has a C-shaped cross-sectional profile in a plane transverse to a path of the groove. a case (24, 224) having an inner side defining a portion of a gas path (22, 122) of the gas turbine engine and an outer side opposite the inner side, the case (24, 224) having an aperture extending from the inner side to the outer side; a sealing member; and a vane disposed in the gas path (22, 122) and comprising: a vane body extending through the aperture; and a vane head disposed at an end of the vane body and disposed outside the gas path (22, 122), the vane head having: an abutting surface contacting an outer surface of the case (24, 224); and a groove receiving the sealing member, the groove surrounding an inner region including the aperture when the vane body extends through the aperture, the groove extending completely around an axis of the aperture and opening to the abutting surface, characterised in that: the groove defines a circumferential path around the aperture axis at a peripheral end of the vane head, the groove is outwardly open relative to the inner region and the aperture axis, and the groove has an inner seating surface receiving the sealing member and hindering movement of the sealing member toward the abutting surface, wherein the inner seating surface has a C-shaped cross-sectional profile in a plane transverse to a path of the groove. a vane body extending through the aperture; and a vane head disposed at an end of the vane body and disposed outside the gas path (22, 122), the vane head having: an abutting surface contacting an outer surface of the case (24, 224); and a groove receiving the sealing member, the groove surrounding an inner region including the aperture when the vane body extends through the aperture, the groove extending completely around an axis of the aperture and opening to the abutting surface, characterised in that: the groove defines a circumferential path around the aperture axis at a peripheral end of the vane head, an abutting surface contacting an outer surface of the case (24, 224); and a groove receiving the sealing member, the groove surrounding an inner region including the aperture when the vane body extends through the aperture, the groove extending completely around an axis of the aperture and opening to the abutting surface, characterised in that: the groove defines a circumferential path around the aperture axis at a peripheral end of the vane head, the groove is outwardly open relative to the inner region and the aperture axis, and the groove has an inner seating surface receiving the sealing member and hindering movement of the sealing member toward the abutting surface, wherein the inner seating surface has a C-shaped cross-sectional profile in a plane transverse to a path of the groove.