;WITH cte AS
ROW_NUMBER() OVER (PARTITION BY MTRL,CODE ORDER BY (SELECT NULL)) AS RN
DELETE FROM cte WHERE RN > 1;
The columns in the PARTITION clause are the columns which you want to delete duplicates of. If you have some ordering scheme that you can use from among the duplicates to decide which one to keep, instead of (SELECT NULL), insert the columns that you would use to order the duplicate rows. The first one in the ordering scheme will be kept.