‘(55) Equal treatment as granted to researchers and students, as well as trainees, volunteers and au pairs when they are considered to be in an employment relationship in the Member State concerned, includes equal treatment in respect of those branches of social security listed in Article 3 of Regulation (EC) No 883/2004 of the European Parliament and of the Council (13). This Directive does not harmonise the social security legislation of Member States. It is limited to applying the principle of equal treatment in the field of social security to the third-country nationals falling within its scope. In addition, this Directive does not grant rights in relation to situations which lie outside the scope of Union law, such as in relation to family members residing in a third country. That should not affect, however, the right of survivors who derive rights from third-country nationals falling under the scope of this Directive, where applicable, to receive survivors' pensions when residing in a third country.
(56) In many Member States, the right to family benefits is conditional upon a certain connection with that Member State since the benefits are designed to support a positive demographic development in order to secure the future work force in that Member State. Therefore, this Directive should not affect the right of a Member State to restrict, under certain conditions, equal treatment in respect of family benefits when the researcher and the accompanying family members are staying temporarily in that Member State.
(57) In the event of mobility between Member States, Regulation (EU) No 1231/2010 of the European Parliament and of the Council (14) applies. This Directive should not confer more rights than those already provided for in existing Union law in the field of social security for third-country nationals who have cross-border interests between Member States.‘