More than 200 families are to ask the French state railway for compensation for its role in transporting Jews to Nazi death camps during World War II.
Between 1942 and 1944 some 76,000 French Jews were deported
The families, from France, Israel, the US, Belgium and Canada, are to send their request to the SNCF this week.
They are asking for several million euros in damages or say they will sue.
In a landmark ruling in June, a court ordered the SNCF and the government to pay damages of 60,000 euros ($80,000, £43,000) for WWII deportations.
The families intend to demand "compensation for the prejudice suffered as a result of [their relatives'] deportation - in livestock wagons, in inhuman conditions, knowing full well that people risked being murdered," one of their lawyers said.
They plan to give the company two months to reply before taking the matter to an administrative court, he added.
Families' requests are being sent ahead of a deadline on 1 September which marks the statutory limitation for filing petitions against the SNCF, he said.
The French railways, who are appealing against the June verdict, argue they had no choice during the war but to do as they were ordered by the Vichy government in collaboration with the German occupying army. Those who refused faced being shot, they said.
The June case was brought by a member of the European parliament, Alain Lipietz, whose father and others were transported to the Drancy camp near Paris - a transit point to the Nazi concentration camps.
They remained there for several months until the camp was freed in 1944.
More than 75,000 French Jews were transported from the camp to death camps in Nazi Germany.
Records show that the SNCF billed the French state for a third-class journey, even though the families were transported in cattle wagons.
The SNCF also carried on demanding the money for the transports after France had been liberated by the Allies.
The argument that the company only followed orders had been accepted by judges in previous cases, who ruled that the SNCF had been commandeered by German forces during the war.
But Mr Lipietz argued that the jurisprudence had changed since 1995, when President Jacques Chirac recognised France's role in the oppression of Jews, and in 1997, when the trial of Vichy official Maurice Papon proved the participation of the government in the deportations.