Quantification and derivation in relative clauses

It is a well-known fact that in Spanish ‘Determiner + Complementizer ’ relative clauses only definite determiners are admitted (in the pre-Comp position), independently of the definite/indefinite nature of the "antecedent " DP, as shown in the following contrast: (1) Buscaba a la/una mujer [con (la) que me pudiera casar] (2) Buscaba a la/una mujer [con (*una) que me pudiera casar] Determiner choice is not affected by the specific/non-specific interpretation of the DP either, which is governed by mood choice (Rivero 1977; Quer 1998). It is not governed by the quantificational force of the antecedent either (existential, cardinal, approximative, etc.) (3) Encontró colegas con los que emborracharse. (4) Me gustan varias playas en las que la arena es fina. Nevertheless, this generalization on the blocking of definite determiners in relative clauses is not completely true if "antecedentless"/"headless " free and amount relatives are considered. These clauses do not seem to exhibit the above restriction: la/una may precede the complementizer in (5). (5) Me casé con la/una [que me puede tolerar] Furthermore, Spanish free relatives are built with the wh element quien, which is claimed to have a