*.name_H-M_alt allows for an alternative Hermann-Mauguin symbol to be given. The way in which this item is used is determined by the user and should be described in the item _space_group.name_H-M_alt_description. It may, for example, be used to give one of the extended Hermann-Mauguin symbols given in Table 4.3.1 of International Tables for Crystallography Vol A (1995) or a full Hermann-Mauguin symbol for an unconventional setting. Each component of the space group name is separated by a space or an underscore. The use of space is strongly recommended. The underscore is only retained because it was used in earlier archived files. It should not be used in new CIFs. Subscripts should appear without special symbols. Bars should be given as negative signs before the numbers to which they apply. The commonly used Hermann-Mauguin symbol determines the space group type uniquely but a given space group type may be described by more than one Hermann-Mauguin symbol. The space group type is best described using the *.IT_number or *.name_Schoenflies. The Hermann-Mauguin symbol may contain information on the choice of basis though not on the choice of origin. To define the setting uniquely use *.name_Hall, list the symmetry operations or generators, or give the transformation that relates the setting to the reference setting defined in this dictionary under *.reference_setting.