together with..., more ~
This pattern expresses that two factors combine to create an intensified or more pronounced result, meaning 'together with...' or 'combined with...'.
と相まって is a formal, written expression used to show that two things work together to produce a stronger effect. It often appears in news, essays, or analytical writing, not in casual conversation. The nuance is that the combination is almost inevitable or natural, leading to a result that is more than the sum of its parts. For example, you can say that a person's effort, combined with talent, leads to success.
When using with nouns, the pattern is straightforward: Xと相まって、Y. It is not used with て-form or ます-stem. The pattern is often followed by a clause that states the resulting intensified state or action.
This pattern is somewhat stiff and literary. In speech, you might hear it in formal presentations or news reports, but in daily conversation, you would say something like ~もあって or ~に加えて instead.