Format of the pseudopotential files (US-RRKJ3):
(a75) titleps                        ! a string
(i5)  pseudotype                     ! the type of pseudo (3 for US)
(2l5) rel, nlcc(is)                  ! rel true for relativistic pseudi
                                     ! nlcc for NLCC
(4i5) mfxcx, mfxcc, mgcx, mgcc       ! indeces of GGA
(2e17.11,i5) zp(is), etotps, lmax(is)! valence charge, total energy, lmax
(4e17.11,i5) xmin(is),rdum,zmesh(is),dx(is),mesh(is) ! the mesh
(2i5) nwfs, nbeta(is)                ! number of wavefunctions and projectors
(1p4e19.11) ( rdum, nb=1,nwfs )
(1p4e19.11) ( rdum, nb=1,nwfs )
do nb=1,nwfs
   (a2,2i3,f6.2) rdum, ndum, lchi(nb,is), oc(nb,is)   ! the l and occupations
                                                      ! of each wavefunction
enddo
do nb=1,nbeta(is)
  (i6) ikk                            ! the point where the beta is zero
  (1p4e19.11) ( betar(ir,nb,is), ir=1,ikk) ! the beta functions
  do mb=1,nb
     (1p4e19.11)  dion(nb,mb,is)      ! d0 coefficients
     if (pseudotype.eq.3) then    
        (1p4e19.11)  qqq(nb,mb,is)    ! q coefficients
        (1p4e19.11) (qfunc(n,nb,mb,is),n=1,mesh(is)) ! augmentation functions
     endif
  enddo
enddo
(1p4e19.11) rdum, ( vnl(ir,lloc(is),is), ir=1,mesh(is) ) ! the local potential
(1p4e19.11) ( rho_at(ir,is), ir=1,mesh(is) )         ! the atomic charge
if ( nlcc(is) ) then
   (1p4e19.11) ( rho_atc(ir,is), ir=1,mesh(is) )     ! the core charge
endif
(1p4e19.11) ((chi(ir,nb,is),ir=1,mesh(is)),nb=1,nwfs) ! the pseudo wavefunctions

All GGA described in the PWSCF code are allowed with this format