“Materialism” is pretty straightfowardly the notion of that physically extent objects and relations to them compose the full extent of describable reality.

For “dialectical”, I turn to Engels’ “Dialectics of Nature”, which is where I think the limitations of treating dialectics as a fundamental law of nature really shines through.

• The law of the transformation of quantity into quality and vice versa;
• The law of the interpenetration of opposites;
• The law of the negation of the negation.

His attempt to work these into scientific phenomena, and Mao’s later attempt to build on this in “On Contradiction” are hot messes, to put it bluntly.