How do I link assets with each other via script in editor?

Hi, I am trying to assign a sprite to a newly created tile via editor script.
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I've tried a few ways.
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Attempt 1

 // create tile
 AssetDatabase.CreateAsset(ScriptableObject.CreateInstance<Tile>(),
                     tilePath);
 
 // assign sprite
 Tile tile = AssetDatabase.LoadAssetAtPath<Tile>(tilePath);
 tile.sprite = AssetDatabase.LoadAssetAtPath<Sprite>(spritePath);

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Attempt 2

 // create tile
 AssetDatabase.CreateAsset(ScriptableObject.CreateInstance<Tile>(),
                         tilePath);
     
 // assign sprite
 AssetDatabase.LoadAssetAtPath<Tile>(tilePath).sprite = AssetDatabase.LoadAssetAtPath<Sprite>(spritePath);

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Both attempts manage to assign a sprite to the created tile BUT the relationship would get removed after a while.
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I'm assuming this is due to GC removing the sprite from memory. Meaning that the assignment was not referenced directly from the asset, but one referenced from memory.
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apologies for the crappy formatting, I have no clue how to add empty lines