A material of the formula SnTiO 3 having a crystal structure comprised of layers, wherein the layers comprise Sn(II) ions, Ti(IV) ions and edge-sharing O 6 -octahedra, the edge-sharing O 6 -octahedra form a sub-layer, the Ti(IV) ions are located within 2/3 of the edge-sharing O 6 -octahedra, thus forming edge-sharing TiO 6 -octahedra, the edge-sharing TiO 6 -octahedra form a honeycomb structure within the sub-layer, the honeycomb structure comprising hexagons with Ti(IV)-vacancies within the hexagons, the Sn(II) ions are located above and below the Ti(IV)-vacancies with respect to the sub-layer, the Ti(IV) ions are optionally substituted with M, M is one or more elements selected from Group 4 and Group 14 elements, and the crystal structure satisfies at least one of the following features (i) and (ii): (i) the Sn(II) ions have a tetrahedral coordination sphere involving three O ions of the layer and the electron lone pair of the Sn(II) ions which is situated at an apical position relative to the three O ions of the layer, (ii) the layers are stacked so that each layer is translated relative to each adjacent layer by a stacking vector S1 or a stacking vector S2, the centers of adjacent hexagons form a parallelogram with a side having a length x and side having a length y, the stacking vector S1 is a combined translation along the side having the length x by 2/3 x and along the side having a length y by 1/3 y, the stacking vector S2 is a combined translation along the side having the length x by 1/3 x and along the side having a length y by 2/3 y, and the crystal structure comprises layers translated relative to adjacent layers by the stacking vector S1 and layers translated relative to adjacent layers by the stacking vector S2. the layers comprise Sn(II) ions, Ti(IV) ions and edge-sharing O 6 -octahedra, the edge-sharing O 6 -octahedra form a sub-layer, the Ti(IV) ions are located within 2/3 of the edge-sharing O 6 -octahedra, thus forming edge-sharing TiO 6 -octahedra, the edge-sharing TiO 6 -octahedra form a honeycomb structure within the sub-layer, the honeycomb structure comprising hexagons with Ti(IV)-vacancies within the hexagons, the Sn(II) ions are located above and below the Ti(IV)-vacancies with respect to the sub-layer, the Ti(IV) ions are optionally substituted with M, M is one or more elements selected from Group 4 and Group 14 elements, and the crystal structure satisfies at least one of the following features (i) and (ii): (i) the Sn(II) ions have a tetrahedral coordination sphere involving three O ions of the layer and the electron lone pair of the Sn(II) ions which is situated at an apical position relative to the three O ions of the layer, (ii) the layers are stacked so that each layer is translated relative to each adjacent layer by a stacking vector S1 or a stacking vector S2, (i) the Sn(II) ions have a tetrahedral coordination sphere involving three O ions of the layer and the electron lone pair of the Sn(II) ions which is situated at an apical position relative to the three O ions of the layer, (ii) the layers are stacked so that each layer is translated relative to each adjacent layer by a stacking vector S1 or a stacking vector S2, the centers of adjacent hexagons form a parallelogram with a side having a length x and side having a length y, the stacking vector S1 is a combined translation along the side having the length x by 2/3 x and along the side having a length y by 1/3 y, the stacking vector S2 is a combined translation along the side having the length x by 1/3 x and along the side having a length y by 2/3 y, and the crystal structure comprises layers translated relative to adjacent layers by the stacking vector S1 and layers translated relative to adjacent layers by the stacking vector S2. <EOS>