It depends on your Modified Adjusted Gross Income.
As you have a 401(k) at work, even for one month, you are considered as covered by a retirement plan at work in 2018.
To determine if you can deduct an IRA contribution, please read this IRS document:
https://www.irs.gov/retirement-plans/plan-participant-employee/2018-ira-contribution-and-deduction-l...
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