SQL Create a new table from a table with a unique combination of two colums

Hi

I have a table called "MARA_MBEW3" that has two columns called ValA and Article. I tried to add a primary key
that combines the two columns Article and  [ValA] using the SQL syntax below but got the error further down
I now want to create a new table that chops out any records that have a duplicate of these two records. How do I do this

ALTER TABLE MARA_MBEW3
ADD CONSTRAINT pk_MARA_MBEW3 PRIMARY KEY (Article, [ValA])
GO

Msg 1505, Level 16, State 1, Line 1
The CREATE UNIQUE INDEX statement terminated because a duplicate key was found for the object name 'Siris1.MARA_MBEW3' and the index name 'pk_MARA_MBEW3'. The duplicate key value is (EI14528, C921).
Msg 1750, Level 16, State 0, Line 1
Could not create constraint. See previous errors.
The statement has been terminated.