An assembly for a gas turbine engine comprising: a case having an inner side defining a portion of a gas path of the gas turbine engine and an outer side opposite the inner side, the case having an aperture extending from the inner side to the outer side; a sealing member ; and a vane disposed in the gas path 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 , the vane head having: an abutting surface contacting an outer surface of the case ; 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 having an inner side defining a portion of a gas path of the gas turbine engine and an outer side opposite the inner side, the case having an aperture extending from the inner side to the outer side; a sealing member ; and a vane disposed in the gas path 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 , the vane head having: an abutting surface contacting an outer surface of the case ; 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 , the vane head having: an abutting surface contacting an outer surface of the case ; 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 ; 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 . <EOS>