Spain's Supreme Court, which has been trying the five men since February, allowed them to leave jail to obtain their formal certificates as elected lawmakers.
Casado and Rivera both accuse Sanchez of betraying Spain for attempting to negotiate with Catalan separatists since he came to power in June.
Secessionists stage protests across the region in response to trials of members of Catalan parliament.
Catalonia declared independence in October 2017, but Spanish authorities stifled the attempt.
The new group, named "The Call", will hold a founding congress Saturday evening, marking the one year anniversary of the secession push.
Spain's conservative prime minister Mariano Rajoy imposed direct rule on Catalonia after last year's unauthorised plebiscite and called early elections.
A poll by the Centro d'Estudis d'Opinio in July shows 46.7% of Catalans surveyed saying they want an independent state, just ahead of 44.9% who do not.
We’re not giving up ... but it will require a different time and a different balance of political forces, Catalan Vice President Pere Aragones said in an interview last week.
La Fageda employs people with mental health conditions, like schizophrenia and bipolar disorder, to help them find purpose in life and greater emotional stability.
Carles Puigdemont will return from Germany after a Spanish judge dropped a European arrest warrant for him.
The new Catalan cabinet was sworn in after months of tensions with the central government, automatically ending Madrid's seven-month rule of the region, imposed by Sanchez' predecessor after separatists declared independence.
Viggo Mortensen has joined Òmnium Cultural.
The Spanish government is attempting to prevent Carles Puigdemont from becoming the leader of Catalonia.
The United Nations Human Rights Committee has publicly backed Jordi Sànchez's right to run for office.
The request comes after protests by independence supporters at the weekend in Berlin and Catalonia calling for Puigdemont's immediate release.
The demonstrations were held as a show of support for the arrested former Catalan president Carles Puigdemont.
German police had earlier arrested Puigdemont as he crossed the border with Denmark by car, responding to a European warrant issued by Spain.
Puigdemont had entered Germany from Denmark after leaving Finland on Friday when it appeared police would arrest him there and launch an extradition process requested by Spain.
Puigdemont, who lives in self-imposed exile in Belgium, had been visiting Finland since Thursday for talks with lawmakers.
Puigdemont has been due to leave Finland on Saturday afternoon, but his exact whereabouts were unknown.
Five people are held in custody, including Catalan presidential candidate Jordi Turull who was due Saturday to seek a second round vote in the regional parliament, after failing to be elected earlier in the week.
Former Catalan leader Carles Puigdemont will speak at the International Film Festival and Forum on Human Rights in Geneva.
During last year's secession crisis in the Spanish region, Vila, who was serving as Puigdemont's business minister, quit the day before Catalan lawmakers made a unilateral declaration of independence on October 27.
Some 45,000 people joined the "Republic Now" march called by the influential pro-independence citizens' group ANC.
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