Mjoin - return multiple columns and concatenate

I have the following Mjoin and want to add another column to be returned. Then concatenate the two returned columns - unit_code and unit_name. Is this possible in the code?

->join(
        Mjoin::inst( 'unit' )
            ->link( 'unit_outcome.unit_outcome_pk', 'unit_unit_outcome_lookup.unit_outcome_fk' )
            ->link( 'unit.unit_pk', 'unit_unit_outcome_lookup.unit_fk' )
            ->order( 'unit.unit_name asc' )
            ->fields(
                Field::inst( 'unit_pk' )
                    ->options( Options::inst()
                        ->table( 'unit' )
                        ->value( 'unit_pk' )
                        ->label( 'unit_name' )              
                    ),
                Field::inst( 'unit_name' )
            )
    )

so something like:

->join(
        Mjoin::inst( 'unit' )
            ->link( 'unit_outcome.unit_outcome_pk', 'unit_unit_outcome_lookup.unit_outcome_fk' )
            ->link( 'unit.unit_pk', 'unit_unit_outcome_lookup.unit_fk' )
            ->order( 'unit.unit_name asc' )
            ->fields(
                Field::inst( 'unit_pk' )
                    ->options( Options::inst()
                        ->table( 'unit' )
                        ->value( 'unit_pk' )
                        ->label( 'unit_name' )              
                    ),
                Field::inst( 'unit_code'  +  '  '  +  'unit_name' )
            )
    )